The term snowball earth refers to the hypothesis that in the distant past, specifically the cryogenian period 850630 million years ago, the earth s surface was entirely frozen from pole to pole. Proponents of the hypothesis argue that it best explains sedimentary deposits generally regarded as of glacial origin at tropical palaeolatitudes and other enigmatic. The presence of such deposits at tropical latitudes is at the core of the snowball earth hypothesis, which is generally accepted for. I give them here because they may be of some interest. Strongly seasonal proterozoic glacial climate in low palaeolatitudes. Today on focus, host david inge talks to paul hoffman, professor of geology at harvard university and one of the leaders of the snowball earth hypothesis. Snowball earth hypothesis university of south alabama. Slushball earth hypothesis, in geology and climatology, a counterpremise to the snowball earth hypothesis. Instability of the southern canadian shield during the late proterozoic. Origins and assessment of snowball earth hypotheses core. Proterozoic low orbital obliquity and axialdipolar. New snowball earth theory could change how we understand. Recall the deglaciation of a snowball earth, sea ice and glaciers disappearing rapidly due to reverse ice.
Various bizarre features in the geological record from 635 and 715 ma ago indicate that the earth underwent some very extreme environmental changes at least twice. Find out how earth s most chilling event took place. Snowball earth seems to have occurred during which of these geological time intervals. Testing the snowball earth hypothesis for the ediacaran. According to the classic snowball earth hypothesis the supergreenhouse drove a hyperactive hydrological cycle inducing intense continental weathering, such that co 2 levels would have been drawn down from very high levels to preglacial levels in about 200 kyrs higgins and schrag, 2003. The properties of the ocean and atmosphere described by the snowball earth hypothesis are not a part of the geologic record. The snowball earth hypothesis nature research paper.
The filamentous microfossils with possible cyanobacterial affinities would suggest photosynthesis did take place during snowball earth, but the leiospheredominated assemblages riedman et al. Evidence for the snowball earth hypothesis in the arabiannubian. Snowball earth and large ice cap instability in the ebm. It would certainly not be a place that most life forms would like to live. Snowball earth is a hypothesis created to offer an explanation about the climate during the neoproterozoic period within the proterozoic ion. Great oxidation event and snowball earth springerlink. Kirschvink suggesting that earth s oceans and land surfaces were covered by ice from the poles to the equator during at least two extreme cooling events between 2. Readings geobiology earth, atmospheric, and planetary. The snowball earth theory, originally proposed by geologist joe kirschvink at the california institute of technology, is based on the premise that the earth was encased in ice between 750. Snowball earth hypothesis, in geology and climatology, an explanation first proposed by american geobiologist j. The snowball earth hypothesis refers to the idea that at some point during the earth s history, specifically during the cryogenian period 850 to 630 million years ago, the entire surface was frozen over, including the oceans. See figure 2 through 5 for an illustration of the four stages of the hoffman and schrag snowball earth hypothesis. The snowball earth hypothesis is controversial among paleontologists, but many believe it helps explain the presence of glacial deposits at tropical latitudes from. The hypothesis was originally developed to explain evidence of the contribution of glaciation to the formation of siltstone whose layered structure and paleomagnetic composition indicated that its sediments were most likely deposited at sea level in the tropics.
Testing the limits of climate change these are my personal notes taken during a geology presentation. Geobiology 20 lecture 12 the climate history of earth. Ppt snowball earth powerpoint presentation free to. Kirschvink suggesting that earth s oceans and land surfaces were covered by ice from the poles to the equator during at least two extreme cooling events. The snowball earth hypothesis essay example graduateway. Hypothesis analysis the sample is a study that analyzes the hypothesis, providing a synoptic distribution, cause explanation, occurrence, and impact, before presenting a personal suggestion based on reflection on the evidence analyzed number of sources. Evidence of a snowball earth comes from the presence of glacial deposits around the world that date back to the cryogenian period 1. Timing of 5 periods of extreme climate in earth s history elements of snowball earth theory evidence for widespread, low latitude glaciations at end of.
The snowball earth hypothesis seh suggests that the earth experienced surface temperatures so low that virtually its entire surface was covered. This collapse can be explained by a global glaciation that is, a snowball earth, which ended abruptly when subaerial volcanic outgassing raised atmospheric carbon dioxide to about 350 times the modern level. The snowball earth event could have been triggered by an increase in oxygen in the atmosphere because it would have resulted in a significant reduction of atmospheric methane level, thereby reducing the greenhouse effect of the atmosphere and causing. The snowball earth hypothesis predicts that the world. Snowball earth hypothesis article about snowball earth. Snowball earth hypothesis february 4, 2008 lucie novoveska late neoproterozoic glaciation 750600 ma paul f. The slushball earth hypothesis, developed by american geologist richard cowen, contends that earth was not completely frozen over during periods of extreme glaciation in precambrian times. The gradual discovery that late neoproterozoic ice sheets extended to sea level near the equator poses a palaeoenvironmental conundrum. Ediacaran siberia was at tropical paleolatitudes when the glacigenic strata of the goloustnaya formation baikal group, siberia were deposited at sea level. The hypothesis that earth was completely covered in ice 635 million years ago has received a serious blow. Once we realized that the snowball hypothesis could explain the. The snowball earth hypothesis wiley online library. By michael schirber, astrobiology magazine august 2015. Snowball earth is a hypothesis created to offer an explanation about the.
The snowball earth hypothesis proposes that during one or more of earths icehouse climates. Snowball earth climate dynamics and cryogenian geologygeobiology. The concept of earth being in an extreme climatic state which resulted in the covering of the earth s surface and oceans in glaciers and ice sheets about 600 million years ago in the neoproterozoic era, which lasted for about ten 10 million years or more, is considered to be the snowball earth hypothesis hoffman and schrag, 2000. Reliable radiometric dating and good paleomagnetic determinations are essential to test the synchronicity and distribution of. Schrag department of earth and planetary sciences, harvard university, cambridge, ma 028, usa introduction in 1987, the caltech biomagnetist and palaeomagnetist joe kirschvink gave undergraduate dawn sumner a rock sample to study for her senior thesis. Research features snowball earth might have been slushy.
Sedimentary challenge to snowball earth nature geoscience. Find materials for this course in the pages linked along the left. Challenges to the hypothesis cowing, keith, snowball earth may not have been that bad after all, discovery channel, may 26, 2000. Moreover, an artificial heat source was introduced to limit ice thickness. The highobliquity hypothesis does not account for major features of the neoproterozoic glacial record such as the abrupt onsets. Learn vocabulary, terms, and more with flashcards, games, and other study tools. Paul hoffman sturgis hooper professor of geology at harvard university. Researchers at harvard university are changing the way we think about earth s largest glaciation event, snowball earth. The snowball earth hypothesis proposes that during one or more of earth s icehouse climates, earth s surface became entirely or nearly entirely frozen, sometime earlier than 650 mya million years ago during the cryogenian period. The existence of a snowball earth climatic episode, implies a frozen earth where ice or snow cover the globe, including at low latitudes.
Kirschvink 1992 identified three principal ways to test the hypothesis. The rapid termination would have resulted in a warming of the snowball earth to extreme greenhouse conditions. This article provides us with a basic understanding of the processes and ideas behind the snowball earth theory. Terra nova 14, 129155 the gradual discovery that late neoproterozoic ice sheets extended to sea level near the equator poses. Do not expect the notes to always be in complete sentences, etc. Magnetic inclinations are consistent with low orbital obliquity and a geocentricaxialdipole magnetic field for most of the past two billion years, and the snowball earth hypothesis accordingly. Imagine a world without liquid water just solid ice in all directions. Other scientists disagree, questioning the earth s ability to thaw and the survival of any life of its surface. The snowball earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago. According to the snowball earth hypothesis, which of these parts of the planet escaped freezing. Snowball earth hypothesis is that the earth was once covered in snow and ice from pole to pole with an average temperature of. The snowball earth hypothesis seh suggests that the earth experienced surface temperatures so low that virtually its entire surface was covered by glaciers andor thick sea ice periodically during its. Thus, a causal relationship between the goe and the snowball earth event has been suggested.