Geology 101 HW 9
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Banded iron formation
are distinctive units of sedimentary rock that are almost always of Precambrian age.
are layered accretionary structures formed in shallow water by the trapping, binding and cementation of sedimentary grains by biofilms of microorganisms, especially cyanobacteria. Stromatolites provide some of the most ancient records of life on Earth.
Basin and Range Province
is a vast physiographic region defined by a unique topographic expression. Basin and Range topography is characterized by abrupt changes in elevation, alternating between narrow faulted mountain chains and flat arid valleys or basins. [Western United States]
or Cambrian radiation was the relatively rapid appearance (over a period of many millions of years), around530 million years ago, of most major animal phyla, as demonstrated in the fossil record, accompanied by major diversification of organisms including animals, phytoplankton, and calcimicrobes.
unique assemblage of soft-bodied organisms preserved worldwide as fossil impressions in sandstone from the Proterozoic Eon at the close of Precambriantime. These fauna represent an important landmark in the evolution of life on Earth: they immediately predate the explosion of life-forms at the beginning of the Cambrian Period 542 million years ago.
That portion of the sea lying upon the continental shelf, and the portions which extend into the interior of the continent with similar shallow depths. Also known as epeiric sea; inland sea.
early Triassic time, an extensive volcanic arc system, called the Sierran Arc began to develop along the western margin of the North American continent. In Southern California, this volcanic arc would develop throughout the Mesozoic Era to become the geologic regions known as the Sierra Nevada Batholith, the Southern California Batholith, and other plutonic and volcanic centers throughout the greater Mojave Desert region.
Pleistocene ice age
the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's recent period of repeated glaciations.
posits that the Earth's surface became entirely or nearly entirely frozen at least once, some time earlier than 650 Myr
Process and timing of the buildup of oxygen [O2]
As early as 3.5 billion years ago, bacteria began to produce oxygen as a waste product of their activity. That oxygen reacted with iron in the ocean to make iron ore. Later, after the iron in the ocean was gone, and the making of iron ore was finished, about 2.5 billion years ago, enough oxygen accumulated for respiration
How did the first continental crust form?
- Continental Crust is felsic or intermediate rock;
- therefore it cannot subduct.
Factors that have probably caused the different mass extinction events that have occurred in the history of life on Earth?
- :the metior, is the biggest 1, It threw up all kinds of stuff, in the air, blocking the sun for many years.
- it could have been an ice age or even a volcanic eruption from the pacific ring of fire causing lose of habitat/ food and over-hunting,
- pollution can also cause extinctions
What is the evidence for the "Snowball Earth" hypothesis ?
- :2 episodes of global ice coverage around 700myr ago and 650myr ago.
- Evidence is the global distribution of glacial sediments, some of which occur on top of tropical limestone sediments.
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