Chapter 34: The Changing Face of the Earth

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(Note: This reading quiz contains some material from lecture that is not found in the textbook.) Energy from the and the earth's motion drives the hydrologic cycle. Most water that evaporates from the surface of the earth rises from the (86%) and falls directly back into the (75%), but weather patterns carry a portion over land where it joins evaporation from the land and falls and flows back to the oceans. The system consists of the rivers, glaciers and groundwater flow. The hydrologic system is constantly changing the face of the earth. Enormous amounts of water flow through the system. It is estimated that it would take about 4 (thousand, million, billion?) years to empty the oceans by evaporation if the system were interrupted so that the cycle could not be completed! During the Great Age, some water was locked into glaciers and sea level dropped about 100 meters. River systems move great quantities of material (sediment). One sees this in great alluvial fans at the bases of mountains, the flood plain of the Ganges River, the Grand Canyon, the Mississippi River flood plain and the Mississippi delta at the Gulf of Mexico. Satellite views show sediment from the great rivers being deposited along continental margins where it bows the strata downward to create a geosyncline. The hydrologic system is literally moving mountains. Glaciers are next to rivers in importance in carving the earth's face. There are two kinds of glaciers, and glaciers. Both have regions of "accumulation" where ice piles up until it can no longer support its own weight, and regions of "ablation" where the ice melts and deposits material it has carried with it. The rough, unsorted debris left behind as a characteristic landform created by moving glaciers is called a . The weight of the larger continental glaciers can cause isostatic (up-down) adjustments of the land elevations that will reroute nearby river systems and also change the way the face of the earth is carved. Groundwater flow is a less important but not insignificant part of the hydrologic system. Actually, the water percolates rather than flows, but may leach out underground caverns. When the water table falls during a drought, the caverns may collapse, leaving (what features?) that create a pock-marked (karst) topography. The wind system (aeolian) also creates some changes on the earth's surface (for example, the extensive sand dunes in the Empty Quarter of Arabia, some of which are 150 miles long.) The hydrologic system is important in understanding the history of the earth because: it move large amounts of material, some of it to the continental margins (edges); the movement of material causes isostatic (up-down) adjustments, sometimes allowing shallow seas to ebb and flow over portions of the continents; it writes and erases the history of the earth. Recap of the History of the Earth: According to the physical evidence, the earth formed about (570 mya, 3.5 bya, 4.5 bya?) ("kya" means thousand years ago, "mya" = million years ago, "bya" = billion years ago), which is the (same, different?) time that the sun formed. In the earliest part of the Precambrian Era, the earth experience heavy and heating. The evidence for the earliest history of the earth is inferred from studies of the (sun, moon, stars?) . The (iron, aluminum, uranium?) catastrophe (about 4.0 bya) began the differentiation of the earth by forming the core of (which element?) and nickel and began to form the atmosphere and hydrosphere. The early atmosphere had very little (element?) . The first evidence of life appears in the fossil record about (66 mya, 570 mya, 3.5 bya?) and thereafter oxygen began to accumulate as plant life (mostly simple algae, etc.) began to multiply. During the Precambrian, a series of as many as (1, 5, 20?) supercontinent(s) seems to have formed and disrupted. The Precambrian came to an end about (66 mya, 245 mya, 570 mya?) and is marked by the (Cambrian, Permian, Jurassic?) Explosion (a worldwide "explosion" of kinds and numbers of life forms.) During the Paleozoic, the supercontinent (name?) came together and formed. The end of the Paleozoic Era is marked by the "First Great " (mass extinction) which occurred about (66 mya, 245 mya, 570 mya?) . Pangaea broke up during the (Paleozoic, Mesozoic, Cenezoic?) Era. The end of the Mesozoic was marked by the Second Great Dying which occurred about (66 mya, 245 mya, 570 mya?) . The (Paleozoic, Mesozoic, Cenezoic?) Era then began and lasted to the present. The (Permian, Jurassic, Pleistocene?) Epoch is the time of a series of recent ice ages, including the Great Ice Age, and lasted from about (3 mya, 66mya, 245 mya?) until 12000-18000 years ago.

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