GEOLOGY

Assignment – The Next Glaciation

Write a one-page paper on the likelihood of another extensive glaciation occurring within the next million years. How about two million years or even 10 million years?

Assignment content/instruction

Provide three scientific reasons/facts from our textbook reading assignment that can be used to support the idea that another glaciation will happen at either 1, 2, or 10 million years from now. [3 points per scientific reason, Total Points = 9]

2.) Provide three scientific reasons/facts from our textbook reading assignment that can be used to support the idea that another glaciation will not happen at either 1, 2, or 10 million years from now. [3 points per scientific reason, Total Points = 9]

3.) Do you think that there will be another extensive glaciation in next one million years? [Total Points = 2]

4.) Do you think that there will be another extensive glaciation in next two million years? [Total Points = 2]

5.) Do you think that there will be another extensive glaciation in next ten million years? [Total Points = 2]

6.) Below, create the reference list of all sources utilized in completing this assignment. Make sure that the reference list is in APA format. And remember, our e-textbook and lecture materials are considered sources. (3 points total)

7.) Make sure that in every response to questions 4 and 5, all sources utilized are cited in APA format. And remember, our e-textbook and lecture materials are considered sources. (0.5 points per question response; 3 points total)

Written Assignment Requirements

Use the Written Assignment Questions provided – these allow us to focus on main concepts for this weeks work utilizing the prompt above.

Your main sources should be our course textbook and online material, as they contain everything you need.

Respond fully to each question, in complete sentences, everything spelt correctly and in your own words.

Must include sources used to complete the assignment by utilizing APA format intext citations in every question response and an APA formatted reference list at the end of the assignment.

More information and guidelines on APA are provided in the Rasmussen APA guide http://guides.rasmussen.edu/apa.

Want to quote from a source?

In the case that you want to quote something from a source, make sure to put quotations “” around the source material COPIED WORD FOR WORD from the source, then put an intext citation after the quoted material in APA format and lastly, include the source in an APA formatted reference list.

If you do not have all three components of APA quoting for COPIED WORD FOR WORD material from a source, then the post can be considered a form of PLAGARISM and can get an automatic ZERO.

Quotations cannot be longer than one or two lines per response, and the quotations must be within the context of your own words, as these written assignments are supposed to be you explaining what you have read and researched.

Chapter 18 Reading

18.1 Glaciers: A Part of Two Basic Cycles Explain the role of glaciers in the hydrologic and rock cycles and describe the different types of glaciers, their characteristics, and their present-day distribution.

Glaciers are a part of two fundamental cycles in the Earth system: the hydrologic cycle and the rock cycle. The water of the hydrosphere is constantly cycled through the atmosphere, biosphere, and geosphere. Time and time again, water evaporates from the oceans into the atmosphere, precipitates on the land, and flows in rivers and underground back to the sea. However, when precipitation falls at high elevations or high latitudes, the water may not immediately make its way toward the sea. Instead, it may become part of a glacier. Although the ice will eventually melt, allowing the water to continue its path to the sea, water can be stored as glacial ice for many tens, hundreds, or even thousands of years.

A glacier is a thick ice mass that forms over hundreds or thousands of years. It originates on land from the accumulation, compaction, and recrystallization of snow. A glacier appears to be motionless, but it is not; glaciers move very slowly. Like running water, groundwater, wind, and waves, glaciers are dynamic erosional agents that accumulate, transport, and deposit sediment. As such, glaciers are among the agents that perform a basic function in the rock cycle. Although glaciers are found in many parts of the world today, most are located in remote areas, either near Earth’s poles or in high mountains.

Valley (Alpine) Glaciers Literally thousands of relatively small glaciers exist in lofty mountain areas, where they usually follow valleys that were originally occupied by streams. Unlike the rivers that previously flowed in these valleys, glaciers advance slowly, perhaps only a few centimeters per day. Because of their setting, these moving ice masses are termed valley glaciers, or alpine glaciers (Figure 18.1). Each glacier actually is a stream of ice, bounded by precipitous rock walls, that flows downvalley from an accumulation center near its head. Like rivers, valley glaciers can be long or short, wide or narrow, single or with branching tributaries. Generally, alpine glaciers are longer than they are wide. Some extend for just a fraction of a kilometer, whereas others go on for many tens of kilometers. The west branch of the Hubbard Glacier, for example, runs through 112 kilometers (nearly 70 miles) of mountainous terrain in Alaska and the Yukon Territory.

Ice Sheets

In contrast to valley glaciers, ice sheets exist on a much larger scale. The low total annual solar radiation reaching the poles makes these regions hospitable to great ice accumulations. Presently both of Earth’s polar regions support ice sheets: Greenland in the Northern Hemisphere and Antarctica in the Southern Hemisphere (Figure 18.2).

Ice Age Ice Sheets About 18,000 years ago, glacial ice covered not only Greenland and Antarctica but also large portions of North America, Europe, and Siberia. That period in Earth history is appropriately known as the Last Glacial Maximum. The term implies that there were other glacial maximums, which is indeed the case. Throughout the Quaternary period, which began about 2.6 million years ago and extends to the present, ice sheets have formed, advanced over broad areas, and then melted away. These alternating glacial and interglacial periods have occurred over and over again.

The only present-day ice sheets are those covering Greenland and Antarctica. Their combined areas represent almost 10 percent of Earth’s land area. (https://goo.gl/JdyThn)

Greenland and Antarctica

Some people mistakenly think that the North Pole is covered by glacial ice, but this is not the case. The ice that covers the Arctic Ocean is sea ice—frozen seawater. Sea ice floats because ice is less dense than liquid water. Although sea ice never completely disappears from the Arctic, the area covered with sea ice expands and contracts with the seasons. The thickness of sea ice ranges from a few centimeters for new ice to 4 meters (13 feet) for sea ice that has survived for years. By contrast, glaciers can be hundreds or thousands of meters thick.

Figure 18.3 Ice shelves

An ice shelf forms when a glacier or an ice sheet flows into the adjacent ocean. Glaciers form on land, and in the Northern Hemisphere, Greenland supports an ice sheet. Greenland extends between about 60 and 80 degrees north latitude. This largest island on Earth is covered by an imposing ice sheet that occupies 1.7 million square kilometers (more than 660,000 square miles), or about 80 percent of the island. Averaging nearly 1500 meters (5000 feet) thick, the ice extends 3000 meters (10,000 feet) above the island’s bedrock floor in some places.

In the Southern Hemisphere, practically all of Antarctica is covered by two huge ice sheets that extend over an area of more than 13.9 million square kilometers (5.4 million square miles). Because of the proportions of these huge features, they are often called continental ice sheets. There is more about Antarctica and its ice sheets in GEOgraphics 18.1. The combined areas of present-day continental ice sheets represent almost 10 percent of Earth’s land area.

These enormous masses flow out in all directions from one or more snow-accumulation centers and completely obscure all but the highest areas of underlying terrain. Even sharp variations in the topography beneath a glacier usually appear as relatively subdued undulations on the surface of the ice. Such topographic differences, however, affect the behavior of the ice sheets, especially near their margins, by guiding flow in certain directions and creating zones of faster and slower movement.

Ice Shelves

Along portions of the Antarctic coast, glacial ice flows into the adjacent ocean, creating features called ice shelves. These large, relatively flat masses of glacial ice extend seaward from the coast but remain attached to the land along one or more sides. About 80 percent of the ice lies below the surface of the ocean, so in shallow water, the ice shelf “touches bottom” and is said to be grounded. In deeper water, the ice shelf floats (Figure 18.3).

There are ice shelves along more than half of the Antarctic coast, but there are relatively few in Greenland. These shelves are thickest on their landward sides and become thinner seaward. They are sustained by ice from the

Figure 18.4 Collapse of an ice shelf These satellite images document the breakup of the Larsen B Ice Shelf adjacent to the Antarctic Peninsula in 2002.

Thousands of icebergs were created in the process. (NASA) adjacent ice sheet, and they are also nourished by snowfall on their surfaces and the freezing of seawater to their bases. Antarctica’s ice shelves extend over approximately 1.4 million square kilometers (0.6 million square miles). The Ross and Ronne-Filchner Ice Shelves are the largest, with the Ross Ice Shelf alone covering an area approximately the size of Texas (see Figure 18.2). In recent years, satellite monitoring has shown that some ice shelves are unstable and breaking apart. For example, during a 35-day span in February and March 2002, an ice shelf on the eastern side of the Antarctic Peninsula, known as the Larsen B Ice Shelf, broke apart and separated from the continent. Thousands of icebergs were set adrift in the adjacent Weddell Sea. The event was captured in satellite imagery (Figure 18.4). This was not an isolated happening but part of a trend related to accelerated climate change. In fact, a 2015 NASA study predicts that the last remnant of the once-vast Larsen B Ice Shelf will break apart by 2020.

Other Types of Glaciers

In addition to valley glaciers and ice sheets, scientists have identified other types of glaciers. Covering some uplands and plateaus are masses of glacial ice called ice caps. Like ice sheets, ice caps completely bury the underlying landscape, but they are much smaller than the continental-scale features. Ice caps occur in many places, including Iceland and several of the large islands in the Arctic Ocean (Figure 18.5).

Often ice caps and ice sheets feed outlet glaciers. These tongues of ice flow down valleys, extending outward from the margins of these larger ice masses. The tongues are essentially valley glaciers that are avenues for ice movement from an ice cap or ice sheet through mountainous terrain to the sea. Where they encounter the ocean, some outlet glaciers spread out as floating ice shelves. Often large numbers of icebergs are produced.

SmartFigure 18.5 Iceland’s Vatnajökull ice cap In 1996 the Grímsvötn Volcano erupted beneath this ice cap, an event that triggered melting and floods. (NASA) (http://goo.gl/RsbHWM).

GEO Graphics 18.1 Antarctica Fact File

Question Is the glacial ice thickest in East Antarctica or West Antarctica? If all of Antarctica’s ice were to melt, about how much would sea level rise?

Figure 18.6 Piedmont glacier Piedmont glaciers occur where valley glaciers exit a mountain range onto broad lowlands.

Piedmont glaciers occupy broad lowlands at the bases of steep mountains and form when one or more alpine glaciers emerge from the confining walls of mountain valleys. Here the advancing ice spreads out to form a broad lobe (Figure 18.6). The sizes of individual piedmont glaciers vary greatly. Among the largest is the broad Malaspina Glacier along the coast of southern Alaska. It covers thousands of square kilometers of the flat coastal plain at the foot of the lofty St. Elias Range. 18.1 Concept Checks Where are glaciers found today? What percentage of Earth’s land surface do they cover? Describe how glaciers fit into the hydrologic cycle. What role do they play in the rock cycle? List and briefly distinguish among four types of glaciers. What is the difference between an ice sheet and an ice shelf? How are they related?

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