cenozoic plate tectonics

ice ages

As the continents moved apart, climate began to cool. When Australia and Antarctica separated, the Antarctic Circumpolar Current could then move the frigid water around Antarctica and spread it more widely around the planet. Antarctica drifted over the south polar region and the continent began to grow a permanent ice cap in the Oligocene. The climate warmed in the early Miocene but then began to cool again in the late Miocene and Pliocene when glaciers began to form. During the Pleistocene ice ages, which began 2.6 million years ago, glaciers advanced and retreated four times (Figure 1.2). During the retreats, the climate was often warmer than it is today. Glacial ice at its maximum during the Pleistocene. These continental ice sheets were extremely thick, like the Antarctic ice cap is today. The Pleistocene ice ages guided the evolution of life in the Cenozoic, including the evolution of humans.

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cenozoic

The Cenozoic began around 65.5 million years ago and continues today. Although it accounts for only about 1.5% of the Earths total history, as the most recent era it is the one scientists know the most about. Much of what has been discussed elsewhere in CK-12 Earth Science Concepts For High School describes the geological situation of the Cenozoic. A few highlights are mentioned here.

evolution of the san andreas fault

The San Andreas Fault has grown where the Pacific and North American plates meet. The plate tectonic evolution of that plate boundary is complex and interesting (Figure 1.1). The Farallon Plate was subducting beneath the North American Plate 30 Ma. By 20 Ma the Pacific Plate and East Pacific Rise spreading center had started to subduct, splitting the Farallon Plate into two smaller plates. Transform motion where the Pacific and North American plates meet formed the San Andreas Fault. The fault moved inland and at present small sea floor spreading basins along with the transform motion of the San Andreas are splitting Baja California from mainland Mexico. This figure shows the evolution of the San Andreas Fault zone from 30 million years ago (bottom) to present (top). Although most plate tectonic activity involves continents moving apart, smaller regions are coming together. Africa collided with Eurasia to create the Alps. India crashed into Asia to form the Himalayas. Click image to the left or use the URL below. URL: Click image to the left or use the URL below. URL:

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plate tectonics

The paleogeography of the era was very much like it is today. Early in the Cenozoic, blocks of crust uplifted to form the Rocky Mountains, which were later eroded away and then uplifted again. Subduction off of the Pacific Northwest formed the Cascades volcanic arc. The Basin and Range province that centers on Nevada is where crust is being pulled apart.

instructional diagrams

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questions

the cenozoic era is defined ad beginning when

-->  a) the dinosaurs and other organisms went extinct at the end of the mesozoic.

b) pangaea broke up.

c) the ice ages began.

d) vertebrates, such as fish, amphibians, reptiles and birds evolved.

early in the cenozoic, blocks of crust uplifted to make this mountain range.

a) the appalachians

b) himalayas

c) the alps

-->  d) the rocky mountains

subduction off of the pacific northwest creates this mountain range.

a) the rocky mountains

b) the san andreas

-->  c) the cascades

d) none of the above

when the east pacific rise subducted beneath north america,

a) the farallon plate split into two smaller plates.

b) the pacific and north american plates met in a transform boundary.

c) the san andreas fault formed.

-->  d) all of these.

africa collided with __ to create the alps.

a) india

-->  b) eurasia

c) antarctica

d) all of the above

when plate motions separated australia and antarctica,

-->  a) the antarctic circumpolar current was free to circle antarctica.

b) the pleistocene ice ages began.

c) surface ocean currents took on an entirely north south direction of motion.

d) all of these.

when antarctica drifted over the south polar region,

a) the climate began to warm.

b) the entire globe cooled as a result

-->  c) the continent began to grow a permanent ice cap.

d) the aurora australis began.

much of human evolution took place during the

a) miocene

-->  b) pleistocene

c) oligocene

d) eocene

during the cenozoic, the continents that had once been part of pangaea

a) began to move back together.

b) have remained stationary.

c) have grown permanent ice sheets.

-->  d) continued to move apart.

during the pleistocene ice age, the glaciers advanced and retreated two times.

a) true

-->  b) false

diagram questions

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