The Cenozoic

The Cenozoic is the uppermost of the three major divisions of the Phanerozoic, the other two being the Mesozoic and Paleozoic (Fig. 1). The term Cenozoic (or Cainozoic) means “recent life”, implying that the fossils encountered in these layers are more similar to modern species. Geologists divide the Cenozoic into three major systems, being, from bottom to top: the Paleogene, the Neogene, and the Quaternary. The Paleogene, is further subdivided into Paleocene, Eocene, and Oligocene, the Neogene into Miocene and Pliocene, and the Quaternary into Pleistocene and Holocene.

geol column

Figure 1: The mayor subdivisions of the geologic column.

Lower Paleocene layers are characterized by low diversity of terrestrial fauna and flora and of marine organisms, but diversity increases upwards through the layers. Plant fossils look very similar to modern species of tropical, sub-tropical and deciduous plants, including cacti and palm trees. Most fossils of mammals are only known from teeth and partial skeletons of small insectivores, herbivores, and carnivores. Most notable are the marsupial mammals, which make up more than 50% of the mammal species in the Paleocene layers of the southern continents.

Eocene fossils are recognizable as having body plans similar to living species. Geologic data suggest that there were no ice caps covering Earth’s poles and that latitudinal differences in temperature were small. Warm climate predominated in many regions of the planet facilitating the growth of large forests on Earth from pole to pole, recorded now as extensive fossil deposits of tropical to subtropical plants even in Arctic regions (Fig. 2). Tropical rainforests grew even in northern latitudes of North America and Europe. Toward the end of the Eocene, the evergreen forests were replaced by grasslands, plains and deciduous trees in North America, Eurasia and the Arctic. Similar changes happened in Antarctica, which became covered with tundra.

Minolta DSC

Figure 2: A perfectly fossilized palm frond associated with fish, from the Eocene Green River Formation, North America. This type of flora is indicative of a more subtropical climate than at present.

The first fossil representative of most of the modern mammal orders appear in the lower layers of the Eocene. A remarkable feature about these fossil mammals is their very small size compared to similar faunas of contiguous Paleocene and Oligocene deposits. Some reptiles, however, were very large, including Titanoboa, a large snake found in South America, and other reptilian megafauna. Birds are also abundant in Eocene layers, as well as fossil insects preserved in amber. Eocene layers also preserve many vertebrate fossils that lived in the oceans, including large carcharinid sharks, Basilosaurus (a large marine mammal), and sirenians.

The Oligocene sedimentary layers preserve a record of decline in temperatures, expansion of ice sheets, and global sea level fall. Important mountain building activity took place during the Oligocene, including areas such as the European Alps and western United States. In general the fossil fauna of the Oligocene, both on land and in the ocean, resembles that of modern organisms, except in South America, where large-sized litopterns, notoungulates and toxodonts (extinct orders of hoofed mammals), and extinct marsupial types lived. Some of these groups are found fossilized even in overlying strata, up to the Pleistocene (Fig. 3).

Miocene deposits record further cooling of the Earth and the extension of ice caps on both hemispheres. The Alps in Europe, the Andes in South America, and the Himalayas in Asia continued to rise, forming some of the greatest mountain ranges in the planet. Extensive grasslands allowed grazers such as horses, rhinoceroses, hippos, ground sloths, and also browsers such as camels, to thrive. All or almost all of the modern bird groups, including marine birds, are present as fossils in Miocene rocks. Marine fossils are abundant, including many specimens of marine mammals and other vertebrates. The abundance of biogenic sediments in Eocene strata indicate that the oceans sustained highly productive communities of microscopic algae (diatoms and other phytoplankton), which formed thick accumulations of diatomaceous sediments containing rich and exceptionally preserved fossils of marine mammals, birds, and reptiles.

Fig 3

Figure 3: A Pleistocene fossil toxodont from Argentina.

Pliocene layers record frequent and significant sea level changes, linked to contraction and expansion of ice sheets. Fossil Pliocene vegetation indicates a reduction of tropical species worldwide. Much of the northern hemisphere was covered by deciduous forests, coniferous forests and tundra, with grasslands spreading on all continents but Antarctica. A significant feature about the Pliocene fauna is gigantism: many species of land habitats were of large size, including mastodons, rodents, ground sloths, armadillos, glyptodonts, etc.

The Pleistocene record is dominated by the effects of glaciations that shaped the landscape in ways still discernible in North America, Russia, and the Nordic countries, as well as in mountain ranges in Asia and Europe. At the last glacial maximum, sea level decreased considerably.

During the Holocene, the global temperature rose and much of the ice that covered the northern hemisphere melted causing rapid sea level rise.

Two trends of interest emerge from this simple review of the Cenozoic fossil record. The first is that the fossil fauna and flora do not differ markedly from what observed today in terms of structure and major higher taxonomic groups. In other words, the type of life documented in Cenozoic layers does not appear to be fundamentally different from what seen in the modern world. The second is the importance played by climate patterns in shaping the geologic record of the Cenozoic, with a major trend for climate deterioration and establishment of glaciation, only recently reversed. Both these macro-scale observations could fit well with a model of the Cenozoic as representing geologic, climatic, and biologic processes unfolding in the post-flood world.

 

By Raul Esperante, PhD

Geoscience Research Institute

Image | Posted on by | Leave a comment

The Mesozoic

Few things in science evoke more interest in children than dinosaurs. Books, films, toys, etc. continue to fuel kids’ interest in the very alien world of our past, yet few Christians know how to respond to their children’s curiosity in a way that is both biblically sound and scientifically accurate. Although a full discussion of the fossils in Mesozoic rocks would require several volumes, a brief synopsis is presented here along with some creationist reflections for those who are interested – parents or otherwise.

066 fix

Skeleton of Tyrannosaurus rex from the Black Hills Institute of South Dakota.

The Mesozoic (“middle life”) Erathem is composed of three systems: the Triassic, Jurassic, and Cretaceous. These Mesozoic rocks make up the middle of the Phanerozoic – the rocks containing most of the fossils we find – sandwiched between the Paleozoic (“old life”) and Cenozoic (“new life”) erathems. As is the case with the rest of the geologic column, the higher one journeys in the column, the younger the rocks are, and the more the fossils within them resemble the life in our present world.

The lowest, and therefore oldest, rocks of the Mesozoic are called the Triassic. The Triassic picks up right after the Permian, the last of the Paleozoic systems. Animal fossils change drastically across the boundary between the Permian and the Triassic, such that evolutionists refer to this as the Permo-Triassic Extinction, thought to be the largest extinction event in earth’s history. Despite the great faunal extinctions, plants go through the P/T Extinction relatively unscathed. This is an interesting phenomenon of the fossil record: plant extinctions and animal extinctions do not seem to line up as would be expected from an evolutionary perspective. Dramatic changes in the flora can be found in the middle Permian and later within the Cretaceous system. The dominant type of plants found in the Mesozoic, up until the Lower Cretaceous, are gymnosperms – plants such as conifers, gingkoes, cycads, and cycadeoids (an extinct group). In the Lower Cretaceous, however, there is an explosive radiation of a completely different type of plant: angiosperms, the flowering plants. Angiosperms dominate our ecosystems today, but they are totally absent from rocks below the Lower Cretaceous – except for some possible Triassic pollen (Hochuli and Feist-Burkhardt, 2013) and a possible Jurassic flower (Liu and Wang, 2015).

What are we to make of the absence of flowering plants – the overwhelmingly dominant form of plant today – in the Triassic and Jurassic? There is almost nowhere you can go on our earth today where you will not find angiosperm pollen. How could the past have been so different? The evolutionist suggests that angiosperms evolved during the Mesozoic from some kind of gymnosperm ancestor, but such transitional fossils are lacking, leaving the event shrouded in mystery. Perhaps, as will be discussed later, the answer lies in segregated ecosystems.

DSC_0615 fix

Skull of a stereospondyl amphibian from the Los Angeles County Museum of Natural History.

The vertebrate animals found in Lower and Middle Triassic rocks would have seemed very foreign to us were we to meet them today, although many of our familiar invertebrates are found in these rocks. There are no crocodiles before the Upper Triassic. Instead, there are crocodile-mimics called phytosaurs and stereospondyl amphibians. There are no large, herbivorous mammals to be found here like cows, sheep, antelope, or deer; rather, we see vast numbers of dicynodonts – tusked and beaked “mammal-like reptiles” – as well as sharply-beaked reptiles called rhynchosaurs. There are no dolphins, seals, or sea turtles – there are dolphin-shaped ichthyosaurs, long-necked nothosaurs, and often turtle-mimicking, clam-crushing placodonts. Instead of armadillos, there are large-reptilian tanks with upturned noses: aetosaurs. There are no birds, frogs, salamanders, or snakes to be found in these rocks.

Then, in the Upper Triassic rocks, there is a sudden change. Several groups make their presence known for the first time in these strata: crocodilians, turtles, dinosaurs, pterosaurs (“pterodactyls”), and even mammals (Bi, et al., 2014). In the Triassic, dinosaurs and dinosaur-like animals are already surprisingly diverse with small and large carnivores and herbivores of various shapes. The pterosaurs, too, are fully-formed and diverse when first found in the record. This is not what we should expect given Darwinian evolution, where a new group should evolve and increase in diversity over time. Instead, we see rapid appearances of new groups in the fossil record, already very diverse.

DSC_0628 FIX

Skull of the mosasar Platecarpus from the Los Angeles County Museum of Natural History.

 

With the start of the Jurassic rocks, most of the bizarre Triassic groups mentioned in the last paragraph have disappeared, except ichthyosaurs and stereospondyls, and even more groups have appeared including lizards and modern amphibians. Dinosaurs are even more diverse in the Jurassic, and some forms get enormous. Notably, the sauropods – dinosaurs like Brachiosaurus, Apatosaurus, and Brontosaurus (now a valid genus again (Tschopp, et al., 2015)) – were the largest land animals to have ever lived, some of which reached lengths over 30 meters! Other new dinosaurs can be found in the Jurassic including armored dinosaurs like Stegosaurus and large carnivores like Allosaurus and Ceratosaurus.

Plesiosaur swimming Paddle

Image: Plesiosaur flipper showing hyperphalangy (the condition of increasing number of phalanges (finger bones) for already existing digits from the South Dakota School of Mines.

Marine rocks suggest oceans teeming with long-necked, four-flipped plesiosaurs and ammonoids with straight and coiled shells. Many new pterosaur types appear in the Upper Jurassic and Lower Cretaceous strata including the filter-feeding ctenochasmatids and the shell-crushing dsungaripterids (Witton, 2013). Notably, the first bird (although maybe not (Xu, et al., 2011; Agnolín and Novas, 2013)) in the fossil record, Archaeopteryx, is found in Middle Jurassic rocks. Although possessing the feathers expected for a bird, it also has several dinosaurian traits including a long bony tail, teeth in its jaws, and clawed hands, evidences which have been used to argue for its transitional state between theropod dinosaurs and birds. Interestingly, many of the most bird-like dinosaurs are found in Cretaceous rocks, and Archaeopteryx and its allies, Anchiornis, Xiaotingia, and Aurornis, seem to show up suddenly in the fossil record with no immediate ancestors.

 

Apart from the appearance of flowers, and their pollinators: bees, in the Cretaceous, this system of rocks is notable for its dinosaur diversity. Large, occasionally-bipedal herbivores like Iguanodon and the duck-billed hadrosaurs dominate Cretaceous ecosystems along with the quadrupedal horned dinosaurs including Triceratops and Centrosaurus. Rarer in the fossil record are the heavily armored ankylosaurs and the bipedal, dome-headed pachycephalosaurs. New theropod groups, including the herbivorous ground sloth-mimicking therizinosaurs, the toothless ostrich-mimics (ornithomimosaurs) and oviraptorosaurs, and the alvarezsaurs, which possessed only one finger on each hand, appear for the first time in the Cretaceous. Small, carnivorous theropods included the famous dromaeosaurs, such as Deinonychus and Velociraptor. The biggest carnivorous theropods are found in the Cretaceous: the tyrannosaurs and the southern hemisphere’s caracharodontosaurids (although Veterupristisaurus is Jurassic (Rauhut, 2011)). Pterosaurs also reached gargantuan sizes, with azhdarchids like Quetzalcoatlus reaching 10-11 meters in wingspan! Despite these enormous animals, the largest Cretaceous mammal is only the size of a Virginia opossum (Hu, et al., 2005). Birds of various kinds, including enantiornithines, are found in many Cretaceous deposits, and mosasaurs – giant, four-flippered sea serpents – dominate the oceans. The first snakes, interestingly possessing four limbs, are also found in Cretaceous rocks (Martill, et al., 2015).

Triceratops skull

Triceratops skull from the Los Angeles Museum of Natural History

Then, with the transition from the Cretaceous to the Paleogene, it all changes. There are no ammonoid, ichthyosaur, plesiosaur, mosasaur, pterosaur, or dinosaur fossils higher than the Cretaceous. Mammals, birds, crocodiles, frogs, lizards, snakes, insects, and other animals continue to be found in Cenozoic rocks, but the absence of the others is a mystery. The most popular explanation in evolutionary circles is that a large asteroid hit the earth, killing the dinosaurs. Smaller animals, such as mammals and birds, were able to survive, whereas the large dinosaurs could not. However, this scenario is obviously too simplistic. Why would the asteroid kill ammonoids, and leave squids? Why did small dinosaurs die when birds did not?

 

Perhaps a better explanation is that the K-Pg boundary represents the end of Noah’s Flood. The Cenozoic, then, represents the recolonization of the earth. Certain animals: dinosaurs, pterosaurs, etc. were unable to survive in the post-Flood world, whereas others were incredibly successful. Perhaps this explains why the Triassic and other systems possess equivalents to today’s animals, rather than our modern forms. Crocodilians and phytosaurs lived in different pre-Flood ecosystems, but after the Flood, the extinction of phytosaurs allowed crocodilians to take over all kinds of compatible ecosystems. Frogs are never found in the Carboniferous or Permian, despite being a place Kermit would love to call home, because there are other animals already in the environments preserved in those systems: microsaurs, dissorophoids, and branchiosaurs. Frogs could have been restricted to certain areas before the Flood, but in the post-Flood world they would have been able to spread themselves all over the world while many other amphibian groups could not and went extinct. Instead of always taking our current world and trying to fit the past into it, maybe we need to recognize that the place outside our windows is the recovery from a worldwide catastrophe, and as such is actually not the norm for earth’s history.

 

M. Aaron

Geoscience Research Institute

 

References

Agnolín, F.L. and Novas, F.E. 2013. Avian ancestors. A review of the phylogenetic relationships of the theropods Unenlagiidae, Microraptoria, Anchiornis, and Scansoriopterygidae. SpringerBriefs in Earth System Sciences: 1-96.

Bi, S., Wang, Y., Guan, J., Sheng, X., and Meng, J. 2014. Three new Jurassic euharamiyidan species reinforce early divergence of mammals. Nature 514: 579-584.

Hochuli, P.A. and Feist-Burkhardt, S. 2013. Angiosperm-like pollen and Afropollis from the Middle-Triassic (Anisian) of the Gemanic Basin (Northern Switzerland). Frontiers in Plant Science 4: 344.

Hu, Y., Meng, J., Wang, Y., and Li, C. 2005. Large Mesozoic mammals fed on young dinosaurs. Nature 433: 149-152.

Liu, Z.-J. and Wang, X. 2015. A perfect flower from the Jurassic of China. Historical Biology. DOI: 10.1080/08912963.2015.1020423.

Martill, D.M., Tischlinger, H., and Longrich, N.R. 2015. A four-legged snake from the Early Cretaceous of Gondwana. Science 349(6246): 416-419.

Rauhut, O.W.M. 2011. Theropod dinosaurs from the Late Jurassic of Tendaguru (Tanzania). Special Papers in Palaeontology 86: 195-239.

Tschopp, E., Mateus, O.V., and Benson, R.B.J. 2015. A specimen-level phylogenetic analysis and taxonomic revision of Diplodocidae (Dinosauria, Sauropoda). PeerJ 3: e857.

Witton, M.P. 2013. Pterosaurs. Princeton University Press, Princeton, New Jersey.

Xu, X., You, H., Du, K., and Han, F. 2011. An Archaeopterx-like theropod from China and the origin of Avialae. Nature 475(7357): 465-470.

Image | Posted on by | Leave a comment

The Paleozoic Rock Record: A Broad Overview of Features and Trends

The rocks of the Earth are like pages of a history book containing information about the past. Geologists who enjoy reading this “book” have found that it consists of two “volumes:” the first, named Precambrian, is mostly devoid of macroscopic fossils. The second, named Phanerozoic, contains layers and sediments providing a rich archive of past forms of animal and vegetal life. The Phanerozoic “volume” is further subdivided in three “sections,” called Paleozoic, Mesozoic and Cenozoic, each consisting of several “chapters” (Fig. 1) [1].

geol column

Fig. 1: The geologic column, with its standard subdivisions, including the Paleozoic and its systems.

This article focuses on the Paleozoic interval of the geologic record. Estimates from global compilations of maps suggest that about 20% of the surface of the Earth is covered by Paleozoic rocks [2]. These rocks are usually well preserved, although mineralogical modifications (e.g., recrystallization) and physical disruption (e.g., faulting and folding) are common. Therefore, Paleozoic rocks represent a substantial and accessible part of the rock record and attempting a comprehensive synthesis of their main characteristics in a blog post is an impossible task. This overview concentrates on selected topics about Paleozoic sedimentary rocks, igneous rocks, fossil patterns, and tectonics. The article will close with some suggestions on the significance form a creationist perspective of salient features and trends in Paleozoic rocks.

 

Paleozoic Sedimentary Rocks

1) Global Stratigraphic Signal. There is a great variety of types represented in Paleozoic sedimentary rocks. However, when looking at the macroscale, certain types of rocks show a specific frequency increase within the Paleozoic or some of its intervals. This non-random pattern of stratigraphic distribution [3] is often observed on a global scale. Examples include: Cambrian sandstone composed almost exclusively of quartz (Fig. 2), found across most of the North American continent and documented on other continents [4]; peaks in abundance of carbonate deposits in the lower and mid-Paleozoic [4, 5], including (for the lower Paleozoic) globally distributed facies such as stromatolites [6] and flat-pebble conglomerates (Fig. 3) [7]; widespread marine black shales, rich in organic carbon, common in the lower Paleozoic and upper Devonian-Mississippian [8]; abundant reef-like deposits in the Silurian and especially in the Devonian [9, 10]; immense coal deposits in the Pennsylvanian and Permian [11]; and extremely wide and thick accumulations of evaporites in the Permian [12].

Minolta DSC

Fig. 2: An example of Cambrian quartzite, consisting of well rounded and well sorted quartz granules. Sawatch Quartzite, Manitou Springs area, Colorado, USA. Penny for scale is 2 cm wide.

fig 3

Fig. 3: An example of Cambrian flat pebble conglomerate, consisting of variously orientated elongated limestone pebbles, several cm in size. Notch Peak Formation, Millard County, Utah, USA. Scale increments are 1cm wide.

2) Widespread Marine Deposition over the Continents. Lower to mid-Paleozoic sedimentary rocks are remarkable in documenting large-scale flooding and establishment of seas over continental interiors. This is perhaps best seen in the North American rock record, where up to four major successive continent-wide flooding phases can be observed in Paleozoic deposits [13]. The topography of the submerged continents must have been very subdued because the layers deposited over the flooded landscape generally show extremely high lateral continuity and flat basal contacts (Fig. 4). In some cases, even thin beds only a few cm thick can be followed laterally for tens of kilometers [14].

 

Minolta DSC

Fig. 4: A classic example of flat contacts between laterally widespread Paleozoic layers. Grand Canyon, Arizona, USA.

3) Upward Increase in Terrestrial Deposits. If it is true that the lower to mid-Paleozoic is dominated by marine deposits even over continental landmasses, terrestrial deposits become substantially more represented in the upper Paleozoic, from the Pennsylvanian upward [15]. In addition, the style of fluvial deposition also appears to differ, with predominantly sheet-like sandy deposits in the lower Paleozoic being complemented from the mid-Paleozoic upward by mud-rich deposits, interpreted as more typical of meandering rivers [16].

 

4) From Low to High Frequency Cyclicity

When tracing rock units along the vertical direction, it is common to see repetitions of certain types of deposits (e.g., sandstone, mudstone, limestone). The cyclical pattern in these rock types reflects changes in the environments of deposition, such as variations in water depth and sediment supply. These changes in rock types, often marked by discontinuity surfaces between packages of layers, are observed throughout Paleozoic sedimentary deposits. However, in the upper Paleozoic (starting from the upper Mississippian) a marked increase in the frequency of these sedimentary cycles is observed on a global scale [17]. Broadly speaking, lower to mid-Paleozoic relatively monotonous deposits are overlain by cyclical successions more intensely punctuated by discontinuities and alternations of different rock types.

 

Paleozoic Igneous Rocks

1) Volcanic Rocks. It is difficult to systematically address global trends in volumes and types of volcanism during the Paleozoic, because of limitations due to the incomplete nature of the rock record. Notably, while basaltic rocks of the ocean floor offer a continuous record of submarine volcanism for the Cenozoic and part of the Mesozoic, only slivers of Paleozoic oceanic crust are preserved. However, Paleozoic rocks do contain a record of some notable episodes of volcanic activity. For example, Upper Ordovician deposits from North America and Europe contain a cluster of ash layers attributed to some of the largest explosive volcanic eruptions ever recorded in the whole Phanerozoic [18, 19]. Large igneous provinces (LIPs), which are regions preserving immense volumes of lava effused within a very narrow stratigraphic interval, have also been documented for the Paleozoic. They include Cambrian, Devonian, and Permian examples, the most spectacular being the Siberian Traps in Russia, where an estimated volume of over 2 million km3 of magma were mobilized at the very end of the Paleozoic [20].

 

2) Plutonic Rocks. Plutonic rocks form from the solidification of magma at depth in the Earth’s crust and constitute the core of the continents. The study of plutonic rocks, therefore, helps to understand the timing and process of formation of the continents. For example, it would be interesting to know how much of the continental crust formed or was recycled during the Paleozoic. Limitations in dating and the incompleteness of the rock record hamper these types of reconstructions. However, some clues can be obtained in indirect ways. Zircon, for example, is a mineral that forms during the crystallization of magma and is very durable and resistant. Even if the original intrusive rock hosting a zircon is eroded, the detrital zircon may survive and be included in younger rocks. Studies looking at the age distribution of detrital zircons indicate that the Paleozoic was one of several intervals with significant crystallization or recycling of crust [21]. Another way to assess the Paleozoic production of plutonic rocks is to look at their preserved surface area compiled from geologic maps. It appears that Paleozoic plutonic rocks are more abundant on the Earth’s surface than their Precambrian or Cenozoic counterparts [22]. This confirms that the Paleozoic was an interval of significant magma emplacement and crystallization.

 

Paleozoic Fossil Patterns

1) Diversity Trends. The most remarkable aspect of the Paleozoic rock record is the abundance of macroscopic animal fossils when compared with underlying Precambrian rocks. This major transition has been called the “Cambrian explosion” and occurs in lower Cambrian strata, where fossils of most animal phyla first appear [23]. An equally important interval is what has been called the Great Ordovician Biodiversification Event (GOBE), referring to a remarkable increase in diversity of marine fossil groups in the Lower to Mid-Ordovician [24]. The Cambrian explosion is unique for the sudden appearance of a large number of new animal body plans, but the GOBE shows the greatest increase in diversity of fossil forms within already known body plans. As a result of these two important stratigraphic intervals, Paleozoic marine faunas can be broadly divided in two groups [25]: the Cambrian fauna (dominated by trilobites) and the overlying Paleozoic fauna (dominated by suspension feeders such as brachiopods, bryozoans, crinoids, and corals) (Fig. 5). These faunas are punctuated by several turnovers at specific stratigraphic levels (e.g., top of Ordovician and, most significantly, top of Permian), where the coordinated disappearance of certain groups is observed [26].

fig 5

Fig. 5: Close up view of a typical example of a lower Paleozoic marine fossil assemblage after the GOBE. Brachiopods, bryozoans, and crinoids make up most of the skeletal fragments seen in the picture. Upper Ordovician Richmond Group, Hueston Woods State Park, Ohio, USA. Scale increments are in cm.

2) Ecological Trends. Along with increased diversity, the GOBE seems to mark a shift to marine faunal assemblages representative of greater ecological complexity [24]. Cambrian layers contain mostly invertebrates that lived on the surface of bottom sediments, but overlying strata include planktonic organisms, fish, burrowers, and suspension feeders that stood taller above the bottom because they were erect. Another important transition is observed in mid-Paleozoic strata, where the fossil record ceases to include only marine organisms and begins to document terrestrial organisms. Macroscopic fossils of land plants first appear in the Silurian and become more common in the Devonian [27], terrestrial invertebrates (including insects, spiders, and millipedes) first appear in the Devonian [28], and a few tracks and remains of land vertebrates first appear in the Devonian [29] but become common in the Carboniferous. Notable groups completely absent from Paleozoic layers are dinosaurs, mammals, birds, and flowering plants.

 

Paleozoic Plate Tectonics

Reconstructions based on paleomagnetism and distribution of major orogenic belts seem to indicate that the initial Paleozoic configuration of continents consisted of four distinct major continental masses, one of which (named Gondwana) grouped all the current continents of the southern hemisphere [30]. Interestingly, whereas most of the margins of these continents show lowermost Paleozoic patterns of sedimentation typical of passive, extensional margins, a remarkable tectonic shift is observed in the Upper Cambrian to Ordovician, where most of these continental margins show evidence for the onset of large scale active convergence [31]. An intriguing aspect of Ordovician plate tectonics is that none of the widespread convergent margins seem to involve collision between continents but only accretion of microcontinents and volcanic arcs, a condition not seen in any other part of the Phanerozoic [32]. A sustained trend of convergence is consistently documented by orogenic belts along continental margins throughout the Paleozoic, resulting in the progressive amalgamation of the different continental masses. Paleogeographic reconstructions indicate that the continents were finally assembled into a supercontinent (named Pangea) by the Early Permian, a configuration that persisted to the end of the Paleozoic [33].

Another feature of interest for Paleozoic plate tectonics is the suggestion of a Cambrian episode of significant true polar wander [34, 35]. This phenomenon implies the redistribution of continental masses with respect to Earth’s axis of rotation resulting in movements of tens of degrees of latitude (e.g., from polar to tropical latitudes) and representing a mechanism of plate motions faster than and different from classic plate tectonics.

 

The Paleozoic: A Creationist Perspective

The existence of a discontinuity in terms of fossil content between the Precambrian and the Paleozoic makes it tempting for creationists to link this horizon to a major discontinuity in Earth’s history. This perception is reinforced when considering that the base of the Paleozoic is often expressed with a physical stratigraphic discontinuity [4] that marks a mechanical-erosional boundary and a significant shift in sedimentary and tectonic conditions [36].

From a biblically informed perspective, a possible candidate to generate such discontinuity would be the global flood of Genesis 6-8. Some Paleozoic sedimentary patterns would fit well on a general level with the description of the biblical catastrophe, in particular the patterns of extensive flooding of continental masses and global signature in the style of sedimentation. Extensive plate rearrangements could also be hypothesized as part of the flood event, and the lowermost Paleozoic presents an interesting interval where both fast plate reorganization and change in predominant tectonic regime seem to be documented. Certainly, plate tectonics offer an important background mechanism to explain several Paleozoic trends. For example, the progressive assembly of Pangea might have controlled the Paleozoic trend in increasing terrestrialization observed both in the sedimentary and fossil record. Interestingly, this parallel increase in preservation of continental deposits and land fossils supports the suggestion of creationists that trends in appearance of fossil groups result at least in part from sampling of different habitats and ecosystems rather than biological evolution. The trend toward a supercontinent configuration might also have played a role in the switch to higher frequency cyclicity observed in the upper Paleozoic sedimentary record, as clastic material from exposed landmasses with extensive drainage systems became more available. Finally, active plate convergence during the Paleozoic would account for the modal peak in Paleozoic igneous rocks, as continental collision settings tend to be favorable for the preservation of new continental crust [37].

In the modern history of creationism, the general consensus about where to place Paleozoic rocks in biblical history has followed an interesting trajectory. The majority of Scriptural geologists, in the first half of the 19th century, assigned the formation of Paleozoic rocks to the time between Day 3 of creation and the onset of the flood [38]. The trend was decidedly reversed in the 20th century, when key figures such as G. Price, H. Clark, H. Morris, and J. Whitcomb clearly interpreted the formation of Paleozoic fossil-bearing rocks as a consequence of the flood [39]. In the past two decades, there has been renewed consideration among some creationists of the possibility that part of the Paleozoic might have been deposited before the flood [40, 41].

Given the immensity of data archived in the Paleozoic rock record, any attempt at a synthetic model from a creationist perspective will have to find the delicate balance between an ability to see the bigger picture without overlooking important details. Before that balance is reached, an exciting work of study and discovery will continue to accompany us in our journey.

Ronny Nalin, PhD

Geoscience Research Institute

 

Endontes

  1. This article adopts the standard geologic column as a reliable indicator of the spatial stratigraphic order of rocks, without endorsing the absolute chronology attached to it. For more on this approach, see our previous blog post Patterns in the fossil record at https://grisda.wordpress.com/2015/07/08/patterns-in-the-fossil-record-part-1/
  2. Dürr, H.H., M. Meybeck, and S.H. Dürr, Lithologic composition of the Earth’s continental surfaces derived from a new digital map emphasizing riverine material transfer. Global Biogeochemical Cycles, 2005. 19(4): p. n/a-n/a. This study estimates that Paleozoic sedimentary and volcanic rocks cover 15.8% of Earth’s surface. However, metamorphic and igneous rocks are not included in the estimate. The undifferentiated cover of metamorphic and igneous rocks is estimated at about 12% of Earth’s surface. Assuming that one third of this 12% of undifferentiated cover is Paleozoic, we arrive at the 20% figure.
  3. For a recent treatment of this feature of the stratigraphic record see Brett, C.E., et al., Time-specific aspects of facies: State of the art, examples, and possible causes. Palaeogeography, Palaeoclimatology, Palaeoecology, 2012. 367–368(0): p. 6-18.
  4. Peters, S.E. and R.R. Gaines, Formation of the `Great Unconformity’ as a trigger for the Cambrian explosion. Nature, 2012. 484(7394): p. 363-366.
  5. Mackenzie, F.T. and J.W. Morse, Sedimentary carbonates through Phanerozoic time. Geochimica et Cosmochimica Acta, 1992. 56(8): p. 3281-3295.
  6. Riding, R., Microbial carbonate abundance compared with fluctuations in metazoan diversity over geological time. Sedimentary Geology, 2006. 185(3–4): p. 229-238.
  7. Kim, J.C. and Y.I. Lee, Flat-Pebble Conglomerate: A Characteristic Lithology of Upper Cambrian and Lower Ordovician Shallow-Water Carbonate Sequences, in Ordovician Odyssey, Short papers, International Symposium on the Ordovician System, 7th, Fullerton, California Pacific Section, SEPM (Society for Sedimentary Geology). 1995. p. 371-374.
  8. Arthur, M.A. and B.B. Sageman, Marine Black Shales: Depositional Mechanisms and Environments of Ancient Deposits. Annual Review of Earth and Planetary Sciences, 1994. 22(1): p. 499-551.
  9. Kiessling, W., Geologic and Biologic Controls on the Evolution of Reefs. Annual Review of Ecology, Evolution, and Systematics, 2009. 40(1): p. 173-192.
  10. Copper, P. and C.R. Scotese, Megareefs in Middle Devonian supergreenhouse climates, in Extreme depositional environments: Mega end members in geologic time, M.A. Chan and A.W. Archer, Editors. 2003, Geological Society of America Special Paper 370 Boulder, Colorado. p. 209-230.
  11. de Sousa e Vasconcelos, L., The petrographic composition of world coals. Statistical results obtained from a literature survey with reference to coal type (maceral composition). International Journal of Coal Geology, 1999. 40(1): p. 27-58.
  12. Warren, J.K., Evaporites through time: Tectonic, climatic and eustatic controls in marine and nonmarine deposits. Earth-Science Reviews, 2010. 98(3–4): p. 217-268.
  13. Sloss, L.L., Sequences in the Cratonic Interior of North America. Geological Society of America Bulletin, 1963. 74(2): p. 93-114.
  14. Brett, C.E., P.I. McLaughlin, and G.C. Baird, Eo-Ulrichian to Neo-Ulrichian views: The renaissance of” layer-cake stratigraphy”. Stratigraphy, 2007. 4: p. 201-2015.
  15. Wall, P.D., L.C. Ivany, and B.H. Wilkinson, Revisiting Raup: exploring the influence of outcrop area on diversity in light of modern sample-standardization techniques. Paleobiology, 2009. 35(1): p. 146-167.
  16. Davies, N.S. and M.R. Gibling, Cambrian to Devonian evolution of alluvial systems: The sedimentological impact of the earliest land plants. Earth-Science Reviews, 2010. 98(3–4): p. 171-200.
  17. Wright, V.P. and S.D. Vanstone, Onset of Late Palaeozoic glacio-eustasy and the evolving climates of low latitude areas: a synthesis of current understanding. Journal of the Geological Society, 2001. 158(4): p. 579-582.
  18. Mason, B.G., D.M. Pyle, and C. Oppenheimer, The size and frequency of the largest explosive eruptions on Earth. Bulletin of Volcanology, 2004. 66(8): p. 735-748.
  19. Sell, B., L. Ainsaar, and S. Leslie, Precise timing of the Late Ordovician (Sandbian) super-eruptions and associated environmental, biological, and climatological events. Journal of the Geological Society, 2013. 170(5): p. 711-714.
  20. Ernst, R.E. and K.L. Buchan, Large mafic magmatic events through time and links to mantle-plume heads, in Geological Society of America Special Papers 352, R.E. Ernst and K.L. Buchan, Editors. 2001: Coulder, CO. p. 483-575.
  21. Voice, P.J., M. Kowalewski, and K.A. Eriksson, Quantifying the Timing and Rate of Crustal Evolution: Global Compilation of Radiometrically Dated Detrital Zircon Grains. The Journal of Geology, 2011. 119(2): p. 109-126.
  22. Wilkinson, B.H., et al., Global geologic maps are tectonic speedometers—Rates of rock cycling from area-age frequencies. Geological Society of America Bulletin, 2009. 121(5-6): p. 760-779. This surface distribution only refers to plutonic rocks that have not been subsequently metamorphosed, therefore excluding orthogneisses or other crystalline rocks derived from a plutonic precursor.
  23. Marshall, C.R., Explaining the Cambrian “explosion” of animals. Annual Review of Earth and Planetary Sciences, 2006. 34(1): p. 355-384.
  24. Servais, T., et al., Understanding the Great Ordovician Biodiversification Event (GOBE): Influences of paleogeography, paleoclimate, or paleoecology. GSA Today, 2009. 19(4): p. 4-10.
  25. Sepkoski, J.J., A Factor Analytic Description of the Phanerozoic Marine Fossil Record. Paleobiology, 1981. 7(1): p. 36-53.
  26. Bambach, R.K., Phanerozoic biodiversity mass extinctions. Annual Review of Earth and Planetary Sciences, 2006. 34(1): p. 127-155.
  27. Edwards, D. and N.D. Burgess, Plants, in Paleobiology: A Synthesis, B. D.E.G. and P.R. Crowther, Editors. 1990, Blackwell Scientific Publications. p. 60-64.
  28. Selden, P.A., Invertebrates, in Paleobiology: A Synthesis, B. D.E.G. and P.R. Crowther, Editors. 1990, Blackwell Scientific Publications. p. 64-68.
  29. Niedzwiedzki, G., et al., Tetrapod trackways from the early Middle Devonian period of Poland. Nature, 2010. 463(7277): p. 43-48.
  30. Meert, J.G. and B.S. Lieberman, The Neoproterozoic assembly of Gondwana and its relationship to the Ediacaran–Cambrian radiation. Gondwana Research, 2008. 14(1–2): p. 5-21.
  31. Boger, S.D. and J.M. Miller, Terminal suturing of Gondwana and the onset of the Ross–Delamerian Orogeny: the cause and effect of an Early Cambrian reconfiguration of plate motions. Earth and Planetary Science Letters, 2004. 219(1–2): p. 35-48.
  32. van Staal, C.R. and R.D. Hatcher, Global setting of Ordovician orogenesis, in The Ordovician Earth System, S.C. Finney and W.B.N. Berry, Editors. 2010, Geological Society of America Special Papers 466. p. 1-11.
  33. Lewandowski, M., Assembly of Pangea: Combined paleomagnetic and paleoclimatic approach. Advances in Geophysics, 2003. 46: p. 199-236.
  34. Kirschvink, J.L., R.L. Ripperdan, and D.A. Evans, Evidence for a Large-Scale Reorganization of Early Cambrian Continental Masses by Inertial Interchange True Polar Wander. Science, 1997. 277(5325): p. 541-545.
  35. Maloof, A.C., et al., Combined paleomagnetic, isotopic, and stratigraphic evidence for true polar wander from the Neoproterozoic Akademikerbreen Group, Svalbard, Norway. Geological Society of America Bulletin, 2006. 118(9-10): p. 1099-1124.
  36. Snelling, A., Earth’s Catastrophic Past: Geology, Creation, & the Flood. 2009, Dallas (TX): Institute for Creation Research, pp. 707-711
  37. Hawkesworth, C., et al., Geochemistry: A matter of preservation. Science, 2009. 323: p. 49-50.
  38. For an in depth historical analysis of scriptural geologists se the series of articles by T. Mortenson available at https://answersingenesis.org/creation-scientists/profiles/british-scriptural-geologists-in-first-half-of-nineteenth-century/
  39. Numbers, R.L., The creationists: From scientific creationism to intelligent design. 2006: Harvard University Press.
  40. Brand, L., Wholistic geology: Geology before, during, and after the biblical Flood. Origins, 2007. 61: p. 7-34.

41.       Gentet, R.E., The CCC Model and its geologic implications. Creation Research Society Quarterly, 2000. 37: p. 10-21.

Posted in Dating and the Age of the Earth, Dinosaurs, Fossils, Genesis Flood, Geological Column, Geology, Philosophical and Historical Perspectives, Plate Tectonics, Uncategorized | Leave a comment

THE PRECAMBRIAN: Part 3 of 3

Because the Precambrian part of geologic history covers so much material, the discussion is split into three parts with this being the third. Here is a summary of the three sections:

  • The first section summarizes the standard model for formation of the Universe, Solar System and Earth, Moon, oceans, continents, and plate tectonics.
  • The second section describes Precambrian rock exposures, as well as the atmosphere, climate, and Precambrian life. Many illustrative pictures are included.
  • This third section provides two perspectives suggested by creationists.

A CREATIONIST PERSPECTIVE

Creationists have two major ways (Roth, 1998) of explaining the Precambrian record: (1) it was mainly formed during the first half of creation week; or (2) the inorganic Earth is actually billions of years old, but then God created life on Earth a few thousand years ago.

First scenario. Those who believe that the entire creation is young note that: it may be inconsistent to explain the earth, light, water, air, land, sun, moon, and stars as created by process over long periods, but explain the birds, fish, animals, and humans as created by fiat in a week; the heavens and starry host were created fiat (Ps 33:6-9) and apparently as part of the six days (Gen 2:1; see also Doukhan, 2004, p.29-32); if the creation is partly old and partly young, then God had one Decalogue (see, Ex 20:8-11) for millions of years and then changed it a few thousand years ago. Personally, this scenario seems to be the most consistent reading of the inspired record.

In this scenario, Andrew Snelling (2009, p.467-470, 613-621) has suggested that the first few days of creation week involved unique inorganic processes not happening today: they exhibited a departure from the laws of thermodynamics, for matter was formed ex nihilo and useful energy increased. Robert Gentry (Gentry, 1988) has used pleochroic haloes as an evidence for the rapid formation of granitic rocks on the third day of creation. Michael Oard (1997) has suggested that any evidence for Precambrian glaciation can be explained in other ways. One summary discussion of this all-young creation can be found at Creation Ministries International.

Snelling (2009, p.321-327) fully recognizes that the Precambrian is a major part of the geologic record. He then emphasizes (p.205-209, 623-627) that during the first day of creation week the Universe, the Earth, light, and the night-day cycle were created. Snelling (p.211-212, 627-629) suggests that the second day of creation week saw the creation of the atmosphere from volcanic gases, interstellar space to hold the sun, moon, and stars, and Earth’s earliest crust from hot magma and hydrothermal fluids from the mantle. The third day (p.213-214, 631-638) brought the creation of the dry land and seas by horizontal and vertical catastrophic plate tectonics at supernatural rates, as well as creation of soils and plants and of cyanobacteria that form stromatolite structures. During the fourth day (p.219-224, 639-641) major tectonic activity could have continued, but primarily God created the sun, moon, and stars to take over the light-giving function.

Second scenario. Those who accept that part of creation may be old and part young note that: angels may have existed before the creation of this world (Job 38:7; Eze 28:12-15); Genesis 1 may not indicate when the angels, stars, sun, moon and Earth (Andreasen 1981) were created; heaven and earth may only refer to the firmament (v.8) and dry land (v.10).

This “old earth / young life” idea (Widmer, 1992; Johnsson, 1993) has not been developed scientifically, but has been briefly outlined by Gorman Gray (2000). This scenario would probably accept much of the standard scientific model outlined above for the inorganic material of the earth. It would probably include long ages of plate tectonic activity with the accompanying earthquakes and volcanoes, and long ages of radioactive decay that are found in Precambrian rocks and could be inherited into more recent rocks by recycling. It would probably only reject the origin of complex life before a recent creation week.

Complex life. In neither of these scenarios would one expect to find evidence of complex life in the Precambrian. Therefore, creationists would dispute the evidence for life in the Precambrian, or attribute the evidence to non-organic processes, or explain it as the result of later organisms invading deep Precambrian rocks (Roth, 1992). However, some creationists might accept the evidence pointing to pre-creation life, since single-celled organisms are not mentioned in the Genesis creation record.

Evolutionists as well would not expect to find complex life in the Precambrian. When asked what evidence might destroy his confidence in the theory of evolution, J. B. S. Haldane reportedly responded with “Precambrian rabbits” as one example. Although not rabbits, at one point it was suggested that angiosperm pollen had been found in the Precambrian, but with further analysis the evidence appeared to be the result of sample contamination (Chadwick, 1981).

The strongest creationist evidence against the standard scientific scenario is based on the difficulty of explaining the origin of life from non-life (Javor, 1998; Horgan, 2011). In addition, the sudden appearance of a great variety of complex life forms in Cambrian rocks, right above the Precambrian, seems difficult to explain in the standard evolutionary paradigm. The Cambrian explosion argument presented by creationists is outlined by The Discovery Institute, The Centre for Intelligent Design, Answers in Genesis, and Creation-Evolution Headlines. The Committee for Skeptical Inquiry presents a counter-response.

Summary. No matter what scenario is accepted, creationists attribute Earth’s geology data to God working either through natural processes or by direct intervention.

 

REFERENCES

Myron Widmer (1992). “Older Than Creation Week?” Adventist Review, August 13, p.4.

Posted in Uncategorized | 1 Comment

THE PRECAMBRIAN: Part 2 of 3

This gallery contains 68 photos.

Because the Precambrian part of geologic history covers so much material, the discussion is split into three parts with this being the second. Here is a summary of the three sections:

The first section summarizes the standard model for formation of the Universe, Solar System and Earth, Moon, oceans, continents, and plate tectonics.
This second section describes Precambrian rock exposures, as well as the atmosphere, climate, and Precambrian life. Many illustrative pictures are included. Design examples and creationist ideas are interspersed throughout.
The third section provides two perspectives suggested by creationists: (1) a young universe and life and (2) old inorganic material, but young life. Continue reading

Gallery | Leave a comment

THE PRECAMBRIAN: Part 1 of 3

SCIENCE AND THE BIBLE TALK ABOUT THE EARLY EARTH

 

INTRODUCTION

How does one relate the standard scientific model to that presented in the Bible for the history of the Universe and Earth? This does not have an easy answer, but the Geoscience Research Institute will be addressing the question in several blogs outlining the different parts of the geologic column. The standard divisions are: Precambrian with little life, Paleozoic with old life, Mesozoic with intermediate life, and Cenozoic with recent life. This blog begins with the Precambrian and is based partly on Biblical Research Institute Science Council presentations and a field trip that occurred in 1993 at Glacier View Ranch south of Rocky Mountain National Park in Colorado.

In the standard chronology of Earth’s geologic history, the Precambrian part covers by far the largest fraction of time – 88% of the total. This spans the time from 4.56 Ga to about 0.54 Ga, where “Ga” stand for giga annum or billions of years ago. The standard scientific timeframe is included because many conservative Seventh-day Adventist academics are comfortable with long ages for inorganic matter and believe that only life was created recently.

Because this article attempts to cover so much material, the discussion is split into three parts. The first two parts present the standard scientific model, where in some cases various models are being suggested for one set of data. Design examples and creationist ideas are interspersed throughout these first two sections. The third part presents some additional creationist perspectives, although not much science is available. (To date young-age creationists have spent little time trying to explain the Precambrian in terms of a recent creation, with little speculation and less scientific research.) Here are the three sections:

  • This first section summarizes the standard model for formation of the Universe, Solar System and Earth, Moon, oceans, continents, and plate tectonics. Brief references to the Universe, Sun, and Moon are included because what happens beyond Earth sets the stage for what happens on Earth during the Precambrian and in the Genesis 1 account.
  • The second section describes Precambrian rock exposures, as well as the atmosphere, climate, and Precambrian life. Many illustrative pictures are included.
  • The third section provides two perspectives suggested by creationists: (1) a young universe and life and (2) old inorganic material, but young life.

Some of the terms and concepts addressed here are too complex to do them justice in a single article. For this reason, many web links and references are included to provide more detail and a more complete understanding. The outline of the standard model is based especially on The Story of Earth by Hazen (2012). Additional information is available from a scholarly volume on Earth’s Oldest Rocks edited by Van Kranendonk et al. (2007). The web provides additional resources such as Encyclopedia Britannica, Michigan State University, Live Science, an historical geology textbook website, a journal devoted to Precambrian Research, a YouTube video, a good summary timescale, and a few cartoons.

UNIVERSE

This is no supermodel spiral

The NASA/ESA Hubble Space Telescope observes some of the most beautiful galaxies in our skies —  This little spiral, known as NGC 4102, has a different kind of appeal, with its tightly-wound spiral arms and understated, but charming, appearance. NGC 4102 lies in the northern constellation of Ursa Major (The Great Bear). 

In the standard scientific model, the universe began at a Big Bang about 14 billion years ago. When an expanding universe was first suggested in about 1930, it was rejected by the scientific community because it seemed to suggest an effect without a cause pointing to an outside force like God. By the 1960s the Big Bang came to be accepted after the observation of microwave background radiation that could be explained by an initially hot, dense universe; however, scientists are still wondering (January 25, 2016) how the universe began and what came before the Big Bang. One creationist suggests that there is a crisis in cosmology (January 26, 2016).

The Big Bang created quarks, which coalesced into protons and neutrons that then formed atoms such as hydrogen and an environment where light could travel through space. These hydrogen atoms clustered into stars which became hot under gravitational pressure and started burning by nuclear fusion, just as in a hydrogen bomb. The “burning” meant combining four protons or hydrogen nuclei (1H) together into helium (4He).

After the hydrogen had been converted to helium, the helium started combining so that three helium nuclei would combine to form carbon (12C), but carbon must have a certain excited-state resonance energy for this to work. Before this resonance energy was experimentally observed, it was predicted by Fred Hoyle as a necessary fact for nature to produce carbon by stellar evolution. Now that this resonance energy has been discovered, it has been suggested as an evidence for the intelligent design of the carbon nucleus, but the argument must be used with caution.

After 12C is produced, heavier elements were formed by the addition of more 4He nuclei to make such elements as oxygen (16O), magnesium (24Mg), silicon (32S), and iron (56Fe). Atoms heavier than iron require an input of energy, so did not form until the extra energy from a supernova explosion was available to produce atoms of iodine, platinum, gold, mercury, lead, uranium, etc. These stellar explosions seeded space with these elements, many of which are just exactly the elements necessary for life.

SOLAR SYSTEM AND EARTH

Remnants of these stellar explosions formed clouds of gas and dust. One such nebular cloud with its mass all rotating in the same direction developed into our Solar System with a large central bulge forming the Sun and the remainder coalescing into planets.

This Sun is the ideal size for life on earth: if it were ten times larger it would burn too fast, and if it were ten times smaller it would not provide enough energy. During Earth’s early stages, the Sun had only about 70% of its current light output. This might suggest a much colder early Earth, but evidence for liquid water at that time indicates that that was not the case. This warmer-than-expected Earth has been explained by a greenhouse effect and by the Earth absorbing a much higher percentage of the Sun’s energy in the past.

A solar wind blew the lighter gases away from the Sun to where the gas planets of Jupiter, Saturn, Uranus, and Neptune now orbit. The heavier material remained closer to the Sun and accreted into meteorites and planetesimals (small planets) and eventually into the rocky planets of Mercury, Venus, Earth, and Mars. This formation of Earth occurred during the period of “heavy bombardment” by meteors in the Hadean (4.5-4.0 Ga). During this time the Earth differentiated into a denser iron/nickel core and less dense silicate mantle. A recent article (January 28, 2016) summarizes a book on the accretion and differentiation of the early Earth.

About 10% of meteorites are iron that once formed the cores of planetesimals and 90% are silica rich chondrites that once formed their mantles. Present day examples of these early meteorites are most easily found in the Earth’s Antarctic ice fields and the Sahara desert. The largest known iron-nickel meteorite is the Hoba meteorite displayed near Grootfontein in Namibia.

MOON

In the standard scientific model, the Moon formed within fifty million years after the development of the Solar System. It was once thought that the Moon formed by the breakup of the Earth, or by being captured from a solar orbit, or by accretion just as the Earth had. New data from Moon rocks in the early 1970s however, indicated that these theories were not satisfactory. The Moon lacked an iron core and volatiles like water, so its composition was too different from that of Earth.

A new model that developed in the mid-1970s postulated that a small planet called Theia once occupied the same orbit as Earth, until it was captured by Earth and annihilated. The collisional debris thrown into space coalesced to form the Moon (see: Slattery, 1995; Choi, 2015). The impact from Theia was just right – not a miss, not too glancing, and not too head-on – and may have caused the Earth’s tilt of 23 degrees. Similar collisions may have caused Venus to rotate backwards and Uranus to rotate sideways. However, a recent article (January 29, 2016) suggests that the Moon was produced by a head-on collision.

Initially the Moon is thought to have orbited the Earth at a distance of about 15,000 miles. At that time the Earth would have rotated on its axis every five hours, a solar eclipse occurred every 84 hours, and the Earth had monster tides. As the Moon moved away from the Earth at about 4 cm per year, the Moon orbited the Earth faster and the Earth’s rotation slowed due to conservation of angular momentum.

OCEANS

Water is ubiquitous in our Solar System in moons and planets, underground oceans and volcanoes. The Moon has subsurface ice and its rocks are 750 parts per million water. Venus had water early in its history, but it was lost due to heat from a runaway greenhouse effect. Mars has a metal core, a silicate mantle, an atmosphere, and a subsurface global ocean hundreds of feet deep. It lost its surface water, but evidence for its past existence is found in water-rich clay, braided stream channels, river valleys, and minerals formed from the evaporation of water. Earth is between these two planets at the ideal distance from the Sun, or “Goldilocks Zone.”

Since the Earth is assumed to have formed from meteorites, the volatiles found in chondrites are expected to have existed in the early Earth – nitrogen, carbon dioxide, sulfur gases, and water. However, a large fraction of the expected volatiles seem to be missing, either lost to space from impacts such as Theia or deeply buried.

Over the last thirty years it has been suggested that Earth’s deep interior may hold prodigious amounts of water. The mantle transition zone may contain as much water as nine times the Earth’s oceans and the lower mantle as much at sixteen times as much. Under the high pressures and temperatures deep in the earth, minerals incorporate hydrogen which, along with their oxygen, can produce water. This water content is evident in granitic magmas that commonly contain 1-4% water and volcanic lavas that cause explosive volcanism as at Mt St. Helens due to the explosive release of pressurized water vapor.

According to the standard model, Earth’s early water came from the volatiles spewed out of volcanoes, so that shallow seas formed within a few tens of millions of years and oceans developed within 100 to 200 million years after Earth’s formation. The early oceans were saltier than today and apparently that salt has precipitated into salt deposits and evaporites – minerals formed from the evaporation of water.

Water has the unique chemical properties necessary for life (Hazen, 2012). Among other properties, it is a solvent; it has high surface tension making capillary action in vascular plants possible; and it splits into hydroxyl (OH) and hydronium (H3O+) ions important for acid/base pH reactions. Its high heat capacity decreases Earth’s temperature fluctuations to a range acceptable for life. Unlike most substances, water expands on freezing; thus ice has a lower density than water and will float. If this were not the case, ocean basins would fill with ice from the bottom up. It is a basic ingredient in biochemical reactions in our bodies that are more than half water.

 

 

CONTINENTS AND PLATE TECTONICS

Over the Earth’s history it has differentiated into a core, a mantle, and oceanic and continental crusts. The crustal plates are formed as magma rises from the mantle at spreading centers and volcanic arcs and destroyed as the tectonic plates descend back into the mantle at subduction zones. The differentiation and movement is due to gravitational effects on different density rock depending on their heat content and the arrangement of atoms in their minerals.

The Earth’s rocks are made up of minerals and the minerals are composed primarily of six types of atoms: oxygen, silicon, aluminum, magnesium, calcium, and iron. One usually thinks of the oxygen in the atmosphere, but 99.99999% of it is in the Earth’s minerals. Silicon is to inorganic rocks what carbon is to organic life, since both form four bonds with surrounding atoms. These oxygen and silicon atoms together (SiO2 silica) are the primary constituents of the Earth and its silicate minerals.

The early Earth was a hot magma ocean with the heat coming from the collision of meteor fragments, from gravity-induced tides, and from radioactive elements. The magma oceans cooled by conduction, convection, and radiation. The hot, early Earth differentiated based on density (in g/cm3) which is related to silica content. Higher silica content means lower density rocks, so rocks nearest the Earth’s surface are generally highest in silica. The differentiated Earth consisted of an iron core with negligible silica and a density of 10-13, a mantle with 45% silica and density of 3-4, and eventually a basalt crust with 50% silica and density 2.8-3.0. For comparison, later granitic rocks have a silica content of 60-75% and a density of 2.6-2.7. Seismology, the study of earthquake waves, is today able to identify a lower mantle made of the mineral perovskite with a density of about 4, a transition zone, and an upper mantle made of peridotite with a density of 3.1-3.4.

During the first 50 to 100 million years, a basalt crust formed from 5% partial melting of the peridotite upper mantle. Rocks don’t have a single melting temperature and the first parts to melt have a higher silica content and a lower density than the remainder. The lower density basalt was more buoyant than the mantle and rose to the surface forming black volcanic islands in the Earth’s shallow seas.

During the Archean from 4.0 to 2.5 Ga, plate tectonic activity began and the first small pieces of granitic continental crust called cratons formed. Life requires atmosphere, oceans, and land, but “You can’t have continents without granite, and you can’t have granite without taking water deep into the Earth … So at some point plate tectonics began and started bringing lots of water down into the mantle. The big question is when did that happen?” (see January 21, 2016 article). John Baumgardner suggests that catastrophic plate tectonics began at the Genesis flood.

The heat energy driving tectonic activity came from convection in the mantle, but the trigger may have been an asteroid impact. This differentiation to granite is part of the trend of elemental separation and concentration: the six major elements separated from hydrogen and helium by the solar wind; Earth’s silicate mantle separated from the iron core; basalt crust separated from mantle; water and other volatiles separated from rock; and now granite separated from basalt. The final result is low density continental crust made up of granitic rocks rich in silica, sodium, potassium, water, and trace elements. Its major minerals are quartz which eventually forms sandy beaches and feldspar which eventually breaks down to clay-rich soil.

The Proterozoic from 2.5 to 0.5 Ga is marked by the onset of modern plate tectonics, including volcanoes and earthquakes. Plate tectonic activity (Condie, 1998; Rino et al., 2004; Hawkesworth et al., 2010) caused the cratons to move around and combine to form the continents and at times a single super-continent. Pangea that formed at about 0.3 Ga is the most familiar example of a super-continent, but is more recent than the Precambrian. Older examples in the Precambrian include Rodinia (1.0-0.6 Ga), Columbia/Nuna (1.9-1.4 Ga), and a more conjectural Kenorland (2.7-2.5 Ga) and Vaalbara (3.1-2.8 Ga). Of these, Andrew Snelling briefly discusses Rodinia in his plate tectonic flood model. The supercontinent cycles are the subject of ongoing study.

REFERENCES

  • Charles Q. Choi (2015). “How the Moon Formed: Violent Cosmic Crash Theory Gets Double Boost.” April 8, 2015.
  • Kent C. Condie (1998). “Episodic continental growth and supercontinents: a mantle avalanche connection?” Earth and Planetary Science Letters, v.163, p.97-108.
  • J. Hawkesworth, B. Dhuime, A. B. Pietranik, P. A. Cawood, A. I. S. Kemp, and C. D. Storey (2010). “The generation and evolution of the continental crust.” Journal of the Geological Society, London, v.167, p.229-248.
  • Robert M. Hazen (2012). The Story of Earth: The First 4.5 Billion Years, from Stardust to Living Planet. Penguin Group: Viking; see also, https://eos.org/articles/new-nova-tv-show-explores-coevolution-of-rocks-and-life
  • Rino, T. Komiya, B. F. Windley, I. Katayama, A. Motoki, and T. Hirata (2004). “Major episodic increases of continental crustal growth determined from zircon ages of river sands: implications for mantle overturns in the Early Precambrian.” Physics of the Earth and Planetary Interiors, v.146, p.369-394.
  • Wayne Slattery (1994 sic). “Where Did the Moon Come From? Part I.” Geoscience Reports, n.18, p.1-3.
  • Wayne Slattery (1995). “Where Did the Moon Come From? Part II.” Geoscience Reports, n.19, p.1-3.
  • Martin J. van Kranendonk, R. Hugh Smithies, and Vickie C. Bennett, eds. (2007). Earth’s Oldest Rocks. Elsevier.

 


Benjamin Clausen, PhD Physics,

Geoscience Research Institute

Posted in Cosmology, Dating and the Age of the Earth, Genesis Flood, Geological Column, Geology, Ice Age, Philosophical and Historical Perspectives, Plate Tectonics | Leave a comment

What Is Biology? Part 4 of 4

How Life is Defined:

There is no simple clear definition of what life is. This is appropriate as life is a wonderful, complex, beautiful, enigmatic phenomenon that defies any effort to over-simplify it. Still, most people have no difficulty recognizing living things and differentiating them from non-living things.

The best that we can do as scientists is list out characteristics that all living things share. If something lacks these characteristics, it is not living, but if it has them, it probably is alive. Here are some characteristics of living things:

  1. Cells – All living things are comprised of cells, ranging from the smallest single-celled bacteria to multi-celled organisms containing trillions of cells, like mature elephants or oak trees
  2. Reproduction – Organisms make copies of themselves
  3. Development and growth – Newly produced living things go through a series of changes, including growth, before they reproduce and continue the cycle of life
  4. Homeostasis – Living things maintain a relatively constant internal environment; not too hot or cold, not to acidic, not too salty, not too dry and so on
  5. Adaptability – This characteristic is sometimes called responsiveness or sensitivity. It means that organisms can detect changes in their environment and respond, within limits, so that they can continue to live
  6. Metabolism – Energy is taken in by living things and used for development, growth, maintenance of homeostasis, reproduction and to adapt to environmental changes.

Most scientists can think of things they would like to add to this list. A molecular biologist might observe that life is complex, an ecologist that life is interdependent, an ornithologist that life is elegant and so on. All these things are true, so why are they not on this list? One reason is that the list could be overly long if everything was on it and verification of every characteristic in every organism could be a daunting task. In addition, some of these things, such as elegance, are judgment calls. Not everyone can agree on what is or is not elegant.

Life is beautifully complicated;reductionism is a commonly used strategy when studying it. Reductionism is the idea that we can better understand things by reducing them to their simplest components. Scientists practicing reductionism are like someone who takes apart machines to see how they work, leaving a trail of irreparable devices scattered in pieces around their home. Imagine trying to understand a bicycle using reductionism. Bikes are wonderfully efficient transportation devices and understanding that may be enough for some people, but reductionists believe that taking bikes apart to examine the wheels, pedals, chain, frame, ball bearings, handlebars and so on will give a better understanding.

The problem with reductionism is that with living things – as with bicycles and other machines – the property we are interested in is the result of all the parts working together, not of the individual parts. In other words, understanding every detail of handlebars really doesn’t tell you how a bike works; it is the arrangement of the handlebars along with the other parts that actually makes them function as handlebars. Off a bike, handlebars are just a bent metal tube.

The phenomenon we call life is an emergent property, something that only exists as a result of a combination of many parts. The parts of a cell are not all a little bit alive. They are no more alive than a rock, just as handlebars are not a little bit a transportation device. They only become part of a transportation device when combined with all the necessary parts of a bike arranged together in exactly the right way.

Biologists have a big problem; life is complicated and hard to understand. Practicing reductionism – taking organisms apart and getting down to their simplest components – seems to be the only way of learning how they work. But life is a product of the complicated interaction of many components, so there is no way of getting down to a few fundamental parts that let us understand how life works or what life is. In other words, life is nothing like as simple as physics or chemistry, in which a few forces or fundamental particles explain a lot. Biology is a whole lot more interesting!

Summary:

Biology is the scientific study of the profound mystery we call life. Life is so amazing that it defies definition and is recognized on the basis of its characteristics, which include: reproduction, development, cellular structure, metabolism, homeostasis and adaptability. Our worldview strongly influences how we see life, the questions we ask about it and the theories we will consider to explain it.

Scientists agree that all theories about nature are subject to empirical data, and can usually agree on what the data are, but science is limited to the data available. Logic sometimes gives multiple interpretations and approaches like reductionism are imperfect. Rules like Ockham’s razor can help, but it should not be surprising that sometimes multiple different conclusions are arrived at based on the same data.

Even with its limitations, and a metaphysical foundation that not everyone would agree to, science, and particularly biology, has proven to be an extraordinary tool for discovery as we seek to understand life and the world in which we live. For those who embrace the biblical worldview, it opens vast new opportunities to see and appreciate the brilliant wisdom of the Creator.


 

Timothy G. Standish, PhD

Senior Scientist, Geoscience Research Institute


 

Posted in Biology, Philosophical and Historical Perspectives | Tagged , , , , , , | Leave a comment