Geo Glaciers
15.5 List and briefly describe five effects of Ice Age glaciers aside from the formation of major erosional and depositional features.
-Large amount of the water trapped by the glaciers from the water cycle -Changes to the valleys and rivers are contributed by the glaciers, obliterating the former valleys and streams -Formed new ones to carry water away from the ice source -Pluvial lakes are formed -Heavy masses of ice cause the down-wrapping of the crust of the Earth
15.3 What are some visible effects of glacial erosion?
1. Availability of rock materials of different sizes with the melting of ice. 2. Deposition of large amounts of sediments at the terminating points of glaciers. 3. Debris of the rock found with the melting of ice which contains various sizes of sediments.
15.3 What factors influence the capability of a glacier to erode?
1. Rate of movement of glacier 2. Thickness of the ice 3. Shape, abundance, and hardness of the rock fragments at glacier base 4. The erodibility of the surface below the glacier
15.2. Relate glacial budget to two zones of a glacier.
A glacial budget is the balance, or lack of balance, between an accumulation at the upper end of the glacier and the loss at the lower end. This loss is termed ablation. There is a balance between the zone of accumulation and the zone of wastage. In the zone of accumulation Snow accumulation and ice formation occur. In the zone of wastage, located below the snow line, here there is a net loss to the glacier as all of the snow from the previous winter melts as does some of the glacial ice.
15.6 About what percentage of Earth's land surface was affected by glaciers during the Quaternary period?
About 30% of the Earth's land area
15.3 How do glaciers acquire their load of sediment?
Acquired by the erosion of the rock, through plucking and abrasion.
15.2 How rapidly does glacial ice move? Provide some examples.
Average rates vary considerably from one glacier to another. Some move so slowly that trees and other vegetation may become well established in the debris that accumulates on the glacier's surface. Others advance up to several meters each day. Examples can be seen within the Antarctic Ice Sheet where portions of some outlet glaciers move at rates greater than 800 meters (2600 feet) per year. On the other hand, ice in some interior regions creeps along at less than 2 meters (6.5 feet) per year.
15.4 Describe the formation of a kettle.
Depressions formed by collapse of drift into voids formed by melting of buried ice blocks
15.4 Contrast end moraine and ground moraine. Relate their formation to the budget of a glacier.
End moraine - till ridge is formed at ending point of glaciers and is like an ice sheet. These are accumulated in the equilibrium state between the accumulation of ice and ablation. Ground moraine - deposits role gently with the receding fronts of ice
15.4 What is an outwash plain? How is it different from a valley train?
End moraine is forming, water from melting glacial falls over till, sweeping some out in front of growing ridge/unsorted debris. Bed load is dropped and meltwater weaves a complex pattern When this happens with an ice sheet, it is an outwash plain. When this happens in a mountain valley, it is a valley train
15.4 How do kames and eskers form?
Eskers - ridges are accumulated due to rivers of melt water which flows in or on the top or below the mass that do not move and stable glacial ice. Kames - melt water of the glaciers erodes the sediments to the openings and depression present in the wastes that are stable present at the ending point of the glacier.
15.3 Relate fiords to glacial troughs.
Fiords - deep and steep-sided inlets found at high altitudes where mountains are present by the ocean. They are glacial troughs which are drowned and sub-merged with the ice
15.4 What term can be applied to any glacial deposit? Distinguish between till and stratified drift.
Glacial Drift Glacial till - poorly sorted unlayered material deposit directly from the glacier Stratified drift - sorted depending on size and weight of particles. Materials not directly deposited but are sorted.
15.1 Where are glaciers found today? What percentage of Earth's land surface do they cover?
Glaciers can be found in many parts of the world today but they are mostly found in remote areas, either near the Earth's poles or in high mountains. Glaciers cover nearly 10% of Earth's land surface.
*15.1 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 fit into the hydrologic cycle because water becomes part of the glacier. Although the ice will eventually melt, allowing the water to continue its path to the sea, where can be stored as glacial ice work many tens, hundreds, or even thousands of years. Glaciers are among the dynamic erosional agents in the rock cycle that accumulate, transport, and deposit sediment. The types of glaciers: Valley (alpine) glaciers A glacier confined to a mountain valley, which had previously been a stream valley Ice sheets Very large thick masses of glacial ice flowing outward in all directions from one or more accumulation centers Ice caps A mass of glacial ice covering a high upland or plateau and spreading out radially Outlet glaciers A tongue of ice normally flowing rapidly outward from an ice cap or ice sheet, Usually through mountainous terrain to the sea Piedmont glaciers A glacier that forms when one or more alpine glaciers emerge from the confining walls of mountain valleys and spread out to create a broad sheet in the lowlands at the base of the mountains Glaciers can be found in many parts of the world today but they are mostly found in remote areas, either near the Earth's poles or in high mountains. Glaciers cover nearly 10&% of Earth's land surface.
15.1 Describe how glaciers fit into the hydrologic cycle. What role do they play in the rock cycle?
Hydrologic cycle: rainfall falls at high regions or high altitudes, becomes part of a glacier. Ice melts, water goes to sea or stored as glacial ice for years Rock cycle: Glaciers also move slowly. They perform things like accumulation, erosion, transportation, and deposition.
15.1 What is the difference between an ice sheet and an ice shelf? How are they related?
Ice sheets are very large thick masses of glacial ice flowing outward in all directions from one or more accumulation centers. An ice shelf is a large, relatively flat mass of floating ice that forms where glacial ice flows into bays and that extends seaward from the coast but remains attached to the land along one or more sides. They are related because an ice shelf is be part of an ice sheet.
15.2 Under what circumstances will the front of a glacier advance? Retreat? Remain stationary?
If ice accumulation exceeds ablation, the glacial front advances until the two factors balance. When this happens the terminus of the glacier is stationary. If a warming trend increases ablation and/or if a drop in snowfall decreases in accumulation, the ice front will retreat. As the terminus of the glacier retreats, the extent of the zone of wastage diminishes. Therefore, in time a new balance will be reached between accumulation and wastage, and the ice front will again become stationary.
15.5 Examine Figure 15.25 and determine how much sea level has changed since the Last Glacial Maximum.
It was about 100 meters lower than today.
15.6 How does the theory of plate tectonics help us understand the causes of ice ages?
Many scientists suggest that ice ages have occurred only when Earth's shifting crustal plates have carried the continents from tropical attitudes to more poleward positions. Plate movement counted for many dramatic climate changes as landmasses shifted in relation to one another and moved to different latitudinal positions. Changes in the oceanic circulation also must have occurred. Climate changes triggered by shifting plates were extremely gradual and happened on a scale of millions of years.
15.6 Briefly summarize the climate change hypothesis that involves variations in Earth's orbit.
Milankovitch's hypothesis explains these oscillations is through variations in Earth's orbit, which lead to seasonal variations in the distribution of solar radiation. The orbit's shape varies (eccentricity), the tilt of the planet's rotational axis varies (obliquity), and the axis slowly "wobbles" over time (precession). These three effects, each of which occur on different time scales, collectively do a good job of accounting for alternating colder and warmer periods during the Quaternary period.
15.5 Compare the two parts of Figure 15.26 and identify three major changes to the flow of rivers in the central United States during the Ice Age.
Missouri River used to flow in the north direction towards the Hudson Bay Mississippi River flows in rout through the centerline Illinois The head of the river Ohio reached-up to Indiana
15.4 How are medial moraines and lateral moraines related? In what kind of setting are these features found?
Moraines-layers or ridges of till Lateral moraines- ridges left along sides of valley In valleys, alpine mountains
*15.2 Describe how glaciers move, the rates at which they move, and the significance of the glacial budget.
Movement of a glacier Glacial ice moves as flow -Plastic flow involves movement within the ice Under pressure, ice behaves as a plastic material -Along the ground, the entire ice mass slides along the ground as basal slip Meltwater acts as lubricant The upper 50 meters of a glacier is brittle and called the zone of fracture Crevasses (cracks in the ice) are present in the zone of fracture but sealed off by plastic flow at depth Rates of glacial movement Like a river, glacial ice does not all move at the same rate Flow is fastest in the center of the glacier Glacial velocity ranges from extremely slow to several meters per day Some glaciers exhibit extremely rapid movements called surges Budget of a glacier -Glacial zones The zone of accumulation is the area where a glacier forms Is located above the snowline -The zone of wastage is the area where there is a net loss of glacial ice: Melting Calving: the breaking off of large pieces of ice (icebergs where the glacier has reached the sea) Glacial budget The glacial budget is the balance, or lack of balance, between accumulation and loss of ice -Loss of ice at the lower end of the glacier is called ablation -If accumulation exceeds loss, the glacial front advances -If ablation increases or accumulation decreases, the glacial front will retreat
15.6 Does the theory of plate tectonics explain alternating glacial/interglacial climates during the Ice Age?
No, the theory of plate tectonic does not.
15.6 Where were ice sheets more extensive during the Ice Age: the Northern Hemisphere or the Southern Hemisphere? Why?
Northern Hemisphere The primary reason is that the Southern polar ice could not spread far beyond the margins of Antarctica.
15.2 Describe two components of glacial movement.
Plastic flow Involves movement within the ice Basal slip Is the process that occurs when the entire ice mass slips along the ground. The lowest portions of most glaciers probably move by this sliding process
15.3 How does a glaciated mountain valley differ in appearance from a mountain valley that was not glaciated?
Prior to glaciated, alpine valleys - "v-shaped" After glaciated, no longer narrow
15.5 Contrast proglacial lakes and pluvial lakes. Give an example of each.
Proglacial lakes - formed due to trapping of glacial meltwater and the blocking of flow of water along the ice margin. Lakes are larger and exist for thousands of years. Examples: Lake Winnipeg, Lake Manitoba, Lake Winni-pegosis, and Lake of the Woods Pluvial lakes - formed in low temperatures and rate of evaporation is low, but the precipitation is moderate. Cool and wet climate. Lake Bonneville
15.6 What was the best source of data showing Ice Age climate cycles?
Sediment core samples from the ocean floor
15.4 Sketch a profile (side view) of a drumlin. Include an arrow to indicate the direction from which the ice advanced.
See this picture
15.3 Describe the features created by glacial erosion in an area where valley glaciers recently existed.
U-shaped; cirques are steep depressions closed on 3 sides and open on the fourth Aretes are narrow, winding, sharp-edged ridges
15.1 List and briefly distinguish among four types of glaciers.
Valley or alpine glaciers: glaciers move slowly, move a few centimeters per day due to their setting Ice sheets: larger than valley glaciers. Flow in all directions from one or more deposits of snow. Ice shelf: very small ice sheets. Top of mountains. Piedmont glacier: found at low lands at bottom of steep mountains.
15.2 What are crevasses, and where do they form?
When the glacier moves over a regular terrain, the zone of fracture is subjected to tension, resulting in cracks called crevasses. These gaping cracks may extend to depth of 50 meters (165 feet). The zone of fracture is the uppermost 50 meters (165 feet) of a glacier
