GLY101 ch 13-15

Which latitudes have sinking air with dry conditions due to atmospheric circulation?

30 & 90: Sinking air naturally forms around 30° north and south, forming large deserts. The poles at 90° also have sinking air, which makes Antarctica the driest continent

What makes the Great Basin unique in North America?

All water drains internally: It is called a basin because all water in the area stays or evaporates, as water does not drain to the oceans.

Which of the following is not influenced by the Coriolis Effect?

Sinking polar air: All but sinking polar air are influenced by the Coriolis Effect. Sinking polar air is caused by the lack of solar energy at such high latitudes, and would happen even if the Earth did not spin

3 cell model of atmospheric circulation, Trade winds, westerly winds, ocean gyres

Because of the Coriolis Effect in the Southern Hemisphere, low pressure systems like hurricanes rotate in which direction? (Think about it!)

The Coriolis Effect causes moving masses to veer to the left in the Southern Hemisphere, thus low pressure storms rotate clockwise; hurricanes rotate counterclockwise in the Northern Hemisphere

Which of the following is formed from a natural version of sandblasting?

Yardangs are sculpted bedrock features produced in the zone of saltating sand.

Why is the rate of weathering and erosion slower in desert regions?

Less water: The lack of water slows both chemical and mechanical weathering.

What is the dominant geologic agent of erosion in most deserts?

Water:Though less abundant in dry climates, water is still the most dominant agent of erosion in most deserts even though wind is an agent of erosion and deposition in some deserts.

What does saltation do to the surface of saltating sand grains?

Rounding and frosting: Saltation causes lots of impacts among grains that produces rounding and frosting of the grain surfaces.

Which dune shape indicates variable and shifting wind directions?

Star

Which desert landscape sequence is in the proper order from young to old?

Alluvial Fan > Bajada > Inselberg: Alluvial fans form first, then combine into bajadas, that eventually bury the eroding bedrock hills to form inselbergs

What feature is most characteristic of dunes?

Cross bedding: It is not always hot and dry conditions that make them but cross bedding forms in all dunes.

What is not a characteristic of ephemeral streams?

are fed by groundwater: Ephemeral streams often carry flash floods, are dry most or part of the year, and flow mainly after rain storms; they receive no water from the water table.

What tectonic process is responsible for the general shape of the Great Basin?

Extension and stretching of the lithosphere:Crustal extension (stretching) produced thinning of the lithosphere and a bowl-like depression of the crust in the Great Basin and Basin and Range.

Precipitated water leaves the Great Basin by:

Evaporation: Water can only get out of the Great Basin by evaporation. There are no streams that flow out to the ocean

The dust bowl in the Midwest of the United States in the 1930s was primarily caused by:

Human errors in judgment: Human errors and conflicts between scientific knowledge and individual judgment caused the dust bowl

Which of these dune types would most likely be associated with limited sand supply and constant wind direction?

Barchan: Barchans or crescent dunes are associated with constant wind direction and limited sand supply.

What is the cause of the Great Basin desert in the southwestern United States?

Rain Shadow and latitude: The rain shadow from mountains like the Sierra Nevada and the fact that it is located near 30° north make the Great Basin desert.

Why does desertification create even more desert in a positive feedback loop?

Arid conditions kill plants and make soil less able to absorb moisture: When a semi-arid desert dries out, plants and soils become even less likely to allow infiltration of groundwater, causing more plant death, more soil drying, and more aridity in a positive feedback loop.

Which of these desert landforms would most likely be associated with salt flats?

Playa: Playa lakes are areas in enclosed basins into which water flows and eventually evaporates, leaving salts behind and forming very flat plains of salt.

Which of these is a product of desert weathering?

Desert varnish: Desert varnish is a dark coating seen on many slowly-weathering rocks in arid conditions.

Which desert landform is most similar to a river delta?

Alluvial fan: An alluvial fan spreads out and slows as stream flow leaves the confines of a steep and narrow canyon, depositing sediment much like a delta.

Why are playas common in the Great Basin of western North America?

Internal drainage: More than anything else, the internal drainage in the Great Basin and the basin and range results in the formation of playas

In the Northern Hemisphere, due to the Coriolis Effect, wind is deflected ________.

to the right: Coriolis deflection is to the right in the Northern Hemisphere; to the left in the Southern Hemisphere.

Which of these is not associated with wind-driven sediment transportation in deserts?

Hoodoo: All but hoodoos, which are erosional features, are related to desert sedimentation and transport.

Saltation, creep, haboob, and sliding stones

What is not included as a cause of the Atacama Desert of South America being so dry?

Intense evaporation: In addition to atmospheric circulation in the Trade Wind latitude and rain shadow, cold ocean currents keep the Atacama dry.

A(n) _______ is confined to a long, narrow valley located in mountainous areas especially closer to the poles.

alpine glacier: There are two general types of glaciers-alpine glaciers and ice sheets. Alpine glaciers form in mountainous areas either at high elevations or near cool and wet coastal areas. A common type of alpine glacier is a valley glacier which is confined to a long, narrow valley located in mountainous areas especially at higher latitudes (closer to either the north or south pole). An ice cap is a smaller version of an ice sheet located on elevated areas.

Which of the following is NOT a glacier?

an iceberg: An iceberg is NOT a glacier because a glacier is moving ice on top of LAND, not floating in the water like an iceberg

The Antarctic ice sheet is up to ________ feet thick!

13,000: The thickest parts of the Antarctic ice sheet are over 13,000 feet thick, over 2.5 miles.

In a glacier, crevasses extend from the surface down to:

near the base of the brittle zone: Crevasses extend through the brittle zone, but die out before the plastic zone

In a cross-sectional view of a glacier, where does the ice actually undergo ductile deformation (i.e. flow internally)?

The lower part of the glacier where stress exceeds 100 kilopascals: In a cross-sectional view of a valley glacier (stress is shown by red numbers on the text figure), the ice will deform and flow where the stress is greater than 100 kilopascals and the extent of that deformation in the lower part of the glacier is depicted by the red arrows. Down slope movement by ductile deformation is shown with blue arrows.

Plastic deformation means that _____.

A material bends or flows when stressed by a force: In the plastic zone ice flows because it is under great pressure of the overlying ice and behaves ductily. This represents the great majority of the ice of a glacier and often contains a fair amount of sediment from boulders to silt and clay. This is called moraine and acts as grinding agents.

What does it mean when a glacier "advances"?

The terminus of the glacier is shifting forward; the glacier is growing longer.: While glaciers are always flowing downslope with gravity, "advance" refers to the position of the end (terminus) of the glacier. If the terminus advances downslope, then the glacier is advancing.

The equilibrium line divides the _________________ from the __________________.

Zone of Accumulation; Zone of Ablation: The equilibrium line (snow line or firn line) divides the Zone of Accumulation where snow accumulates and compresses into glacier ice from the Zone of Ablation where melting and sublimation take place.

Which of the following will not promote glaciers to advance?

Global warming: We are in an interglacial of the recent Ice Age and glaciers would likely be advancing now or in a few centuries except for global warming, which is causing glaciers worldwide to retreat. In many parts of the world, glaciers may be gone in students' lifetimes!

Cirque:

form at the heads of glaciers where plucking at the headwall steepens it and creates a semicircular amphitheater-like basin.

Terminal Moraine:

A terminal moraine is a large pile of till (unsorted sand, gravel, boulders, and clay) deposited by the end (terminus) of a glacier. In the associated image, there are also lateral (side) and medial (middle) moraines.

Hanging Valley

Hanging valleys occur where a glacial tributary met the main glacier which was usually larger and eroded more deeply. Hanging valleys often have picturesque water falls.

What is the main cause of the glacial cycles during the last Ice Age?

Milankovitch Cycles: Milankovitch Cycles are periodic changes in the Earth's orbit and rotation axis and caused the glacial-interglacial cycle of 41,000 years from 2.5 to 1.0 million years ago and a longer cycle of ~100,000 years from 1.0 million years ago to today. These correlate well with Ice Age cyclic evidence.

What happens to land level and sea level when glaciers melt?

Isostatic rebound and sea level rise: When ice melts off the land, the land rises due to isostatic rebound, and sea level rises due to meltwater reentering the ocean

When was the peak of the last glaciation?

26,500 to 19,000 years ago: The last of the advances of ice sheets, known in popular media as "The Ice Age" but known by geologists as the last glacial maximum, reached its peak between 26,500 and 19,000 years ago.

Under current conditions of climate change, glaciers are retreating at what rates?

Years and decades: Global warming due to human burning of fossil fuels is causing glaciers and ice sheets to lose in years an amount of mass that would normally take centuries. Many glaciated places may be devoid of glaciers in today's students' lifetimes!

The Antarctic ice sheet has been there for several million years. What has happened to the Antarctic continent as a result?

Parts of the continent have been isostatically depressed below sea level.: The weight of the ice presses down on the continent isostatically depressing parts of it below sea level.

Tarn:

A basin hollowed out by the weight of thicker ice at the head of the glacier may be later occupied by a beautiful mountain lake called a tarn.

What causes striations and glacial polish on bedrock?

Grains of rock embedded in the ice grind against the bedrock.: polishing it and grooving striations into it.

Horn:

produced where several glaciers' cirques erode a bedrock peak to a sharp point.

Which of the four seasons controls the glacial budget and is most responsible for glacial advance and retreat?

Summer is the controlling season. Cool summers promote glacial advance and warm summers promote glacial retreat.

This image shows a trunk glacier flowing toward the viewer. Looking at the front of the picture, how many tributary glaciers have joined to form this trunk glacier?

5: Counting the ice streams clearly separated by medial moraines, there are 5 separate tributary glaciers. In the far right ice stream, there is a hint of a medial moraine separating a minor stream but 5 substantial streams are clearly indicated.

What caused Lake Bonneville to form?

less evaporation and more precipitation: Lake Bonneville was a pluvial lake, formed by changes in the climate. The more humid climate during the ice age provided water for the glaciers and pluvial lakes. When the climate changed back to 'normal' (i.e. today's climate), evaporation increased and precipitation decreased.

What happens at the base of a glacier?

The ice slides over bedrock on a thin film of meltwater.: Because of pressure melting of ice (opposite of decompression melting of rising asthenosphere), the base of the glacier slides over bedrock on a thin film of meltwater.

What is the most immediate and visible evidence that a valley has been occupied by a glacier?

The valley is quite straight with a broad bottom, and is U shaped: After glaciation, the valley is quite straight, with a broad bottom and U shape. Upon entering the valley, these would be the most immediate and obvious evidence.

The atmosphere is mostly composed of _________.

Nitrogen- 78%

The Sun mostly emits this type of radiation.

The sun emits a broad spectrum of radiation including visible light as well as infrared and ultraviolet. It is how these wavelengths of radiation interact with the gasses in the atmosphere that causes the greenhouse effect and the warming of the Earth.

Which best explains how sunlight can easily pass through the atmosphere, but heat energy radiated from the Earth's surface has a harder time escaping the atmosphere?

Each specific wavelength of radiation interacts differently with atmospheric gases.: Different atmospheric gases interact with different wavelengths of radiation so solar radiation (mostly visible light and UV radiation) mostly passes through the atmosphere. But at the surface it changes into heat energy or thermal infrared radiation. This thermal infrared radiation comes off the surface as heat energy and since it has a longer wavelength, it is absorbed and trapped by greenhouse gases.

The carbon dioxide levels today are around ________.

410 ppm: The NOAA animation called "Atmospheric CO2" and the Mauna Loa CO2 Observatory show the measured concentration now to be around 410 ppm, an exponential increase since 1958's measurement of 315 ppm!

Over the last 800,000 years, the highest pre-industrial concentration of carbon dioxide in atmosphere was _____.

approximately 300 ppm: The NOAA animation "Atmospheric CO2" shows historical levels based on ice core records do not exceed 300 ppm over the last 800,000 years. Current measured values of over 410 ppm produced in only 50 years is dramatic evidence that human fossil fuel burning is the primary cause.

If sea ice melts, what happens to sea-level and why?

Sea level will NOT change if sea ice melts because the volume of sea ice is already accounted for in the ocean (it's floating). However, on land glaciers do affect sea level

Climate has changed in the past. What has caused the series of major climate fluctuations on the thousand-year time scales of the last 5 million years?

Milankovitch cycles: Milankovitch cycles are cyclical changes in the Earth's orbit and rotational axis that affect how the earth receives and absorbs solar radiation and are associated with the thousand-year time scales of the cycles of the Ice Age.

What do tree rings tell us about paleoclimate?

periods of wetter and dryer climate from the width of the rings: Tree rings are used to determine and correlate wetter and dryer climates in a region over the lives of the trees.

Why are planktonic microfossils like foraminifera so useful as proxy indicators of ancient climate?

Their fossils in sediments reveal assemblages that were adapted to different water temperatures.:Microfossils like foraminifera were adapted to different water temperatures and changes in fossil assemblages in a sequence of sediments show changes in water temperatures.

Which sector of the economy produces the most anthropogenic greenhouse gas emissions?

electricity and heat production: Electricity and heat production account for the largest proportion of anthropogenic greenhouse gases at 25%.

Which oxygen isotope, used in paleoclimatology, combined with hydrogen in water is more easily evaporated and thus would be found more concentrated in glacial ice?

O-16: O-16 and O-18 are the two most common isotopes used in paleoclimatology. O-16 is lighter and in water (H2O) is preferentially evaporated and concentrated in glaciers. Therefore, ocean water during a glaciation (ice age) and sea life making carbonate shells from it are enriched in O-18 while glaciers are enriched in O-16

When did global anthropogenic carbon dioxide emissions from fossil fuels, cement, and flaring start increasing rapidly?

1950: While the Industrial Revolution of around 1800 is when we started burning fossil fuels in greater amounts, around 1950 is when anthropogenic carbon emissions started increasing very rapidly.

Which of the following is an example of a proxy indicator of climate change?

Chemical signatures from ancient marine biota or ice used to estimate temperatures for the past 800,000 years.: A proxy indicator is an indirect estimate of past climate, often spanning many thousands to millions of years. They are most commonly chemical signatures from ancient marine shells in deep sea sediments or from ice cores.

Which of the following best describes how deep sea sediment cores are used as proxy indicators of past climate?

Oxygen isotope ratios from microfossil shells in the sediments gives proxy information about past climates.: The regular layering of sediments in the ocean accumulates microfossil shells made of calcite (CaCO3) as organisms die and sink. The oxygen in the shell carbonate which is drawn from the seawater can be analyzed for oxygen isotope ratios which are a proxy indicator of water temperatures and ice volume on land.

What is a Positive Feedback Mechanism?

a natural process whose result increases the process: A Positive Feedback Mechanism is a natural process whose result increases the process itself. Examples of PFM include permafrost melting (which releases CO2 and methane that then increases melting), loss of Arctic sea ice (which reduces albedo and retains more solar heat), and melting of glaciers and ice sheets (which also exposes more low albedo land). They each produce consequences that continue to increase global warming. Positive Feedback Mechanisms are of great concern to earth scientists because lack of understanding of their threshold points and continuing human activity may allow humankind to trigger them beyond our ability to control the outcomes!

Which is the best illustration of the greenhouse effect?

Sunlight passing through a car window and heating up the inside of the car.: Sunlight passing through a car window and heating the inside of the car to a high temperature is a good example of the greenhouse effect. Solar energy warms the earth's surface and certain "greenhouse gases" in the atmosphere trap infra-red (heat) radiation from the earth's surface warming the atmosphere.

Which of the following best describes how ice cores are used as proxy indicators of past climates?

The ice accumulating in annual layers traps air bubbles of the ancient atmosphere that reveal atmospheric composition in the past.: Ice cores preserve annual layers of ice as the snow precipitates and accumulates; this ice has air bubbles trapped in it. These bubbles have the same composition as the atmosphere at the time the ice formed, so it becomes a record of the composition of the atmosphere from the past.

With regard to climate change, a greenhouse gas is an atmospheric gas that _______?

Absorbs and traps heat radiating from the surface of the earth.: A greenhouse gas absorbs and traps heat radiating from the surface of the earth causing the atmosphere to warm.

According to continuous measurements of atmospheric CO2 at the Mauna Loa CO2 Observatory, levels of CO2 in the atmosphere have reached and are surpassing what amount?

410 ppm: While it has reached and surpassed all lower values, CO2 has now reached 410 ppm, the highest level for millions of years, and continues to climb. And the rate of climb is increasing exponentially!

What does the Keeling Curve show?

The exponential increase in atmospheric CO2 since 1958: Charles Keeling established a CO2 observatory to make regular measurements of atmospheric CO2. These measurements at the Mauna Loa Observatory in Hawaii are posted in a graph bearing his name called the Keeling Curve, which shows the increase and the variation of these values from season to season since 1958. Atmospheric CO2 continues to increase at an exponential rate! Current CO2 values are dramatically higher than at any time in the last 800,000 years!

What percent of the additional heat caused by human activities is being absorbed by the oceans?

80%-90%: The ocean covers 70% of the Earth's surface and because the water is deep and circulates, it can absorb a huge amount of energy. The oceans absorb 80%-90% of the heat human activities are adding to the atmosphere. This slows the burning of the earth's surface, but that added heat is stored in the oceans because of the high specific heat of water. It has many negative affects including increasing ocean acidity and the number and intensity of hurricanes!

According to a 2004 study published in the prestigious journal of Science, what percentage of climate scientists agree that warming is from human activities?

97%

Which best describes the most damaging to life (of the many negative effects) of the ocean becoming more acidic?

Marine organisms with shells of calcium carbonate are having a harder time extracting CO3 from seawater to secrete their shells.: Marine organisms like foraminifera, corals, mollusks and other organisms with calcium carbonate shells are having a harder time secreting their shells. Increasing extinction is a real possibility for these important organisms!