Wednesday March 23, 2011 (Ice Ages) (Period 5 Only: Video and Quiz – Oceans, Earth’s Last Frontier)

The Launch Pad Wednesday, 3/23/11 Identify the following glacial depositional features. A B A. lateral moraine B. end moraine

The Launch Pad Tuesday, 3/22/11 Identify the following glacial depositional features. eskerkame

The Launch Pad Tuesday, 3/22/11 Identify the following glacial depositional features. kettledrumlin

The Launch Pad Tuesday, 3/22/11 Identify the following glacial depositional features. valley trainoutwash plain

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Assignments For This Six-WeeksDate IssuedDate Due Video Quiz - Lakes, Rivers, and Other Water Sources 2/27 WS - Running Water and Groundwater (Part 1) 2/253/4 PowerPoint Project – Rivers (P5 only) 2/283/3 WS - Running Water and Groundwater (Part 2) 3/23/9 Video Quiz - Groundwater3/3 Cornell Notes - Ice3/83/9 WS - Ice3/93/25

Ice

Indirect Effects of Ice Age Glaciers As the ice advanced and retreated, animals and plants were forced to migrate. This led to stresses that some organisms could not tolerate. Ice Age Glaciers of the Past

Indirect Effects of Ice Age Glaciers In areas that were centers of ice accumulation, such as Scandinavia and northern Canada, the land has been slowly rising for the past several thousand years. The land had downwarped under the tremendous weight of almost 2-mile thick masses of ice. Following the removal of this immense load, the crust has been adjusting by gradually rebounding upward ever since. Ice Age Glaciers of the Past

Indirect Effects of Ice Age Glaciers A far-reaching effect of the Ice Age was the worldwide change in sea level that accompanied each advance and retreat of the ice sheets. The snow that nourishes glaciers ultimately come from moisture evaporated from the oceans. Therefore, when the ice sheets increased in size, sea level fell and the shoreline moved seaward. Estimates suggest that sea level was as much as 330 feet lower than it is today. Ice Age Glaciers of the Past

Indirect Effects of Ice Age Glaciers The formation and growth of ice sheets was an obvious response to significant changes in climate. But the existence of the glaciers themselves triggered climatic changes in the regions beyond their margins. In arid and semiarid areas on all continents, temperatures were lower, which meant evaporation rates were also lower. At the same time, precipitation was moderate. This cooler, wetter climate resulted in the formation of many lakes called pluvial lakes. Although most are now gone, a few remnants remain, the largest being Utah’s Great Salt Lake. Ice Age Glaciers of the Past

A successful theory for the causes of glaciation must account for the cooling of the Earth, as well as short-term climatic changes. Some proposed possible causes for glaciation include plate tectonics, the fact that the continents were arranged differently, and changes in oceanic circulation. Another suggested cause involves variations in Earth’s orbit. Causes of Glaciation

This Earth-orbit hypothesis was first developed by the Serbian scientist Milutin Milankovitch and is based on the premise that variations in incoming solar radiation are a principal factor in controlling Earth’s climate. Milankovitch formulated a comprehensive mathematical model based upon the following elements: Variations in the shape (eccentricity) of Earth’s orbit about the Sun Changes in obliquity – that is, changes in the angle that the axis makes with the plane of Earth’s orbit The wobbling of Earth’s axis, called precession Changes in climate over the past several hundred thousand years are closely associated with variations in Earth’s orbit Causes of Glaciation

Orbital Variations A. The shape of Earth’s orbit changes during a cycle that spans about years. It gradually changes from nearly circular to one that is more elliptical, and then back again. This diagram greatly exaggerates the amount of change. B. Today, the axis of rotation is tilted about 23.5 o to the plane of Earth’s orbit. During a cycle of years, this angle varies from 22 o to 24.5 o. C. Precession. Earth’s axis wobbles like that of a spinning top. Consequently, the axis points to different spots in the sky during a cycle of about years.

Figure 6.24A Eccentricity

Figure 6.24B obliquity

Figure 6.24C

Variations in Earth’s orbit correlate with the timing of glacial cycles. However, these orbital changes do not adequately explain the magnitude of the temperature changes that occurred during the most recent Ice Age. Other factors must also have contributed. One factor involves variations in the chemical composition of the atmosphere. Other influences involve changes in the reflectivity of Earth’s surface and in ocean circulation. Other Factors as Causes of Glaciation

Chemical analysis of air bubbles that became trapped in glacial ice indicate that the Ice Age atmosphere contained less carbon dioxide and methane than the post-Ice Age atmosphere. As the concentration of CO 2 and CH 4 gases increase in the atmosphere, the global temperature rises. Other Factors as Causes of Glaciation

Ice and snow reflect a large portion of solar energy back into space. Thus, energy that would have warmed Earth’s surface and the air above is lost and global cooling is reinforced. Other Factors as Causes of Glaciation

Studies suggest that the warm current that transports large amounts of heat from the tropics toward higher latitudes in the North Atlantic was much weaker during the ice ages. This would lead to a colder climate in Europe, amplifying the cooling attributable to orbital variations. Other Factors as Causes of Glaciation Research has shown that ocean circulation changes during ice ages.

Video and Quiz Oceans – Earth’s Last Frontier Period 5