Geog 1250 exam 2

alluvial fans

"alluvial" refers to sediments transported and deposited by rivers, so alluvial fans are sediments deposited in a fan shape by river flow. They are particularly prominent in deserts (where they are not obscured by vegetation), but they can be found in all environments. In these photos of Death Valley

longitudinal profile

. Rivers tend to adjust their longitudinal profiles through erosion and deposition to produce a smooth, concave upward profile that is steep in the headwaters and has a gentle slope (or gradient) downstream near its outlet As the river system erodes, lowering its longitudinal profile, there is a limit to how much lowering can take place because water cannot flow uphill. a cross-sectional image showing the variation in the river's elevation along its length

How are pluvial lakes related to glacial periods? The Great Salt Lake is the remnant of pluvial Lake ____?

1. Is the desert evaporation increases 2. It is remnant of pluvial lake Bonneval Although pluvial lakes are not caused by glaciation, they may become more numerous during glacial periods when the climate cools, allowing rainfall to accumulate without evaporating

Why are lakes short-lived features? How did Crater Lake, Oregon form? Is it still active?

1. They are drained by stream erosion, filled with sediment, climate warming 2. Crater Lake was formed by Mt. Mazama; It is still active a caldera formed by volcanic activity

What is responsible for producing the long, linear lakes in east Africa? Why is the Aral Sea shrinking?

1. the tectonic 2. The Aral Sea is shrinking because of the withdrawals for irrigation

About how much of the earth's land surface is covered by glacial ice today? Where? During the last ice age?

10 percent of land area on Earth is covered with glacial ice, including glaciers, ice caps, and the ice sheets of Greenland and Antarctica. Glacierized areas cover over 15 million square kilometers (5.8 million square miles). 30% coverage during the last ice age

cap rock

A necessary part of an oil trap. The cap rock is impermeable and hence keeps upwardly mobile oil and gas from escaping at the surface

What was the weather like in the southeastern U.S. during the 1993 flood on the Mississippi River?

A rainy autumn in 1992 resulted in above-normal soil moisture and reservoir levels in the Missouri and Upper Mississippi River basins. During the winter of 1992-93, the region experienced heavy snowfall. These conditions were followed by persistent spring weather patterns that produced storms over the same locations. Soils across much of the affected area were saturated by June 1, meaning instead of soaking into the ground, additional rainfall all flowed into streams and rivers. These wet-weather conditions contrasted sharply with the droughts and heat waves experienced in the southeastern United States

river terraces

After a meandering river has created a wide flood plain and uplift then causes the river to begin cutting down a feature that might be a formed is a

horn

As several cirques erode toward the mountain top, they produce a pyramid-shaped peak called a horn matterhorn grand tetons wyoming

oxbow lake

As the bends become more and more accentuated, individual meanders are eventually isolated from the main channel to become cut-off meanders, or oxbow lakes.

Why should estimates of the 100-year flood discharge be viewed with skepticism?

Based on historical record, confidence intervals are very large, a single large flood can cause the 100-year flood discharge to increase dramatically, and although it is unlikely that a 100 year flood will occur in any single year, the chances are pretty good that one will occur in the long-term

glacial till

Because glaciers move like conveyor belts, they carry the rock materials they have eroded (called glacial till) and eventually deposit them at the ice margin to form moraines, which are ridges of glacial till.

moraines

Because glaciers move like conveyor belts, they carry the rock materials they have eroded (called glacial till) and eventually deposit them at the ice margin to form moraines, which are ridges of glacial till.

What kind of glacial feature is Long Island, New York?

Continental Glaciers (Apart of the terminal moraines) part of a terminal moraine left behind by the Laurentide Ice Sheet.

calderas

Crater Lake, Oregon, is a caldera formed by volcanic activity. Overall, this process does not produce very many lakes

dendritic pattern

Drainage network patterns This type of branching is similar to what we find elsewhere in nature, for example, the branching of tree branches, veins in leaves, our nervous system, our system of arteries, the passageways in our lungs. In drainage basins, the dendritic pattern forms in uniform geological materials. *most basic

pluvial lakes

During glacial periods in North America, the cooler climate allowed the Laurentide Ice Sheet to expand southward. This cooling, however, also affected areas not directly in contact with the ice. In the Great Basin region of Nevada and neighboring states, a tremendous expansion in the number and size of lakes occurred. are supplied by increases in rainfall associated with the cooler conditions. The Great Basin contains many closed basins that do not drain to the ocean. So, when the climate cooled, there was less evaporation which allowed rainwater to accumulate in these basins. Even Death Valley had a 1000 foot deep lake, Pluvial Lake Manly. Although pluvial lakes are not caused by glaciation, they may become more numerous during glacial periods when the climate cools, allowing rainfall to accumulate without evaporating.

How does flood seasonality differ in the southeastern U.S.?

Encourages convergence/mid-latitude in spring/winter tropical in summer

Describe the differences between flashy and non flashy hydrographs

Flashy-low infiltration environment (steep slopes, impermeable soil, intense rainfall, sparse vegetation) Non-flashy-high infiltration environment (gentle slope, permeable soils, low intensity rainfall, dense vegetation

Why is summer temperature so important in determining whether glacial ice will accumulate?

Ice sheets are formed from snow. Because an ice sheet survives summer, the temperature in that location usually does not warm much above freezing. In many locations in Antarctica the air temperature is always well below the freezing point of water. If the summer temperatures do get above freezing, any ice core record will be severely degraded or completely useless, since meltwater will percolate into the snow.

What happens to sea level during ice ages? During warm periods when the ice sheets melt?

Ice sheets that form during glaciations cause erosion of the land beneath them. After some time, this will reduce land above sea level and thus diminish the amount of space on which ice sheets can form. This mitigates the albedo feedback, as does the lowering in sea level that accompanies the formation of ice sheets. This realigned the thermohaline circulation in the Atlantic, increasing heat transport into the Arctic, which melted the polar ice accumulation and reduced other continental ice sheets. The release of water raised sea levels again, restoring the ingress of colder water from the Pacific with an accompanying shift to northern hemisphere ice accumulation.

playa

In deserts, dry lake beds called playas are common. They may contain water briefly, but it usually evaporates quickly. What is left behind is a salty, mud-cracked, flat surface. The Racetrack Playa shown on the next slide is found in an isolated part of the desert near Death Valley, California. It's mud-cracked surface contains rocks that have apparently slid across the playa, leaving behind trails As it turns out, it is thin sheets of ice that are pushed by the winds, causing the rocks to move.

How did the position of the jet stream affect the flood-producing rainfall in the Mississippi River basin in 1993?

Jet stream was stuck in one pattern and produced a trough that encouraged mid-latitude cyclones. It also produced a ridge/high pressure and produced dry areas near the Carolinas

In the lower 48 states, where are most of the glaciers located?

Mount Rainer in Seattle/Cascades

meander scar

Over time the oxbow lakes fill in completely with sediment to become meander scars that are usually visible from the air.

suspended load

Sediment is transported in 3 modes load consists of smaller particles that the flow is capable of transporting fully in suspension. The suspended load make the water appear muddy

overland flow

Surface runoff into streams

recurrence interval

The 100-year flood is a return period or recurrence interval. It states the probability that a flood of a certain size will occur. How do we estimate recurrence intervals? Well, we start with discharge measurements, like those at the gauge on the Tar River in Greenville. The US Geological Survey (USGS) monitors discharge at thousands of gauging stations across the US. Each year, they take the largest discharge of the year (called the 'annual flood') and plot it on a graph like that shown on the next slide. So if we have 25 years of discharge measurements, then we will have 25 dots on the graph slide 40 chapt 6

What are the names of the ice sheets that expanded in North America and Europe during the last ice age?

The Laurentide Ice Sheet was almost 3 kilometers (2 miles) thick and covered North America from the Canadian Arctic all the way to the modern U.S. state of Missouri. Glacial retreat of the Laurentide Ice Sheet created such features as the Great Lakes. The glaciers on Baffin Island, Canada, are remnants of the Lauentide Ice Sheet. The Scandinavian Ice Sheet dominated Western Europe. It once spread as far west as the island of Great Britain and as far east as Moscow, Russia. It originated in the Jostedalsbreen area of southern Norway, where it eventually retreated. Jostedalsbreen remains the largest glacier in Europe today.

hanging valley

The main valleys deepen more rapidly than the tributary U-shaped glacial valleys, leaving the tributary valleys hanging above the main valley floor. Streams in these hanging valleys produce waterfalls

Why were the largest continental ice sheets located in the northern hemisphere during the last ice age?

The primary reason is that the Southern polar ice could not spread far beyond the margins of Antarctica.

base level

This lower limit is base level. The ultimate base level is sea level. Local base levels may also be imposed by very resistant rocks that the river cannot erode rapidly.

U-shaped valley

V-shaped valleys are scoured by glaciers to produce U-shaped glacial valleys. Sierra Nevada California yosemite valley V shaped half dome el capitan three sisters

How does water velocity vary in river channel

Velocity varies horizontally and vertically

wilting point

When field capacity is reached, plants withdraw capillary water, eventually only hygroscopic water remains. This is the wilting point. At this point only hygroscopic water remains, which is unavailable to plants.

deltas

When rivers empty into quiet bodies of water (i.e., lakes or the ocean), the decrease in stream flow velocity induces deposition of a delta Delta shape is also influenced by ocean currents, wave action, and human activities. Nile river delta

tarn

When the glaciers melt away, the cirques contain small lakes called tarns. The strings of stair-stepped lakes downstream from a tarn are called paternoster lakes

fjiord

a U-shaped valley near the coast that has been flooded by post-glacial rise in sea level. tierra del fuego coastline

point bars

a crescent-shaped accumulation of sand and gravel deposited on the inside of a meander The erosion of the cut bank is balanced by the deposition of sediment on the inside of the meander bend in a deposit called the point bar

Field capacity

ability of a soil to hold water against the downward pull of gravity Following a precipitation event that saturates the soil, the gravitational water will drain from the soil under the force of gravity. When all the gravitational water has drained, the field capacity is reached

cut bank

also known as a river cliff or river-cut cliff, is the outside bank of a water channel (stream), which is continually undergoing erosion. Cut banks are found in abundance along mature or meandering streams, they are located on the outside of a stream bend, known as a meander, opposite the slip-off slope on the inside of the bend

driftless area

an area (as in Wisconsin and parts of Minnesota, Illinois, and Iowa) that is free from glacial drift and seems not to have been covered by the Pleistocene ice.

braided channels

consist of multiple channel threads that are caused by in-channel bars and islands that divert flow in multiple directions. These channels are generally steep and wide compared to meandering channels. Braiding is often an adjustment to an abundant supply of coarse sediment (i.e., bedload). Environments where braided channels may be found include deserts ( which often have an abundance of coarse particles) and downstream from glaciers (glaciers typically supply a lot of sediment).

What general effects do continental glaciers have on the landscape when the ice melts away? Alpine glaciers?

continental: Gently undulating topography leave behind terminal or end moraines that mark the different positions of the ice margin. Areas between ice lobes form interlobate moraines. When large blocks of ice that remain finally melt, they leave behind depressions that become lakes called kettles. Alpine: Angular/rugged/ icebergs

continental glaciers

cover large areas and override much of the underlying topography. The ice sheets currently found in Greenland and Antarctica are examples. the largest continental glaciers are called the Laurentide ice sheet in North America and the Scandinavian ice sheet in Europe originated in what is now Hudson Bay, while the Scandinavian ice sheet originated in Bohemian Bay. The Earth's crust remains depressed in both locations due to the tremendous weight of the ice

How does the Driftless Area differ from the rest of the state of Wisconsin?

deeply carved river valleys -where there were no glaciers, no till could be deposited

natural levees

during floods when sediment is carried out of the channel and deposited on the floodplain. Because more sediment settles out quickly near the channel, the channel banks are built up more rapidly than the part of the floodplain far from the channel

Gravitational water

fills macro pore spaces. Gravitational water is not available for plants and is held very weakly in the soil.

Capillary water

fills micro pore spaces in the soil. Capillary water is the only form that plants can withdraw.

trellis pattern

found in areas with folded sedimentary rocks, that consist of alternating layers of resistant rocks and less resistant rocks. Valleys form in the less resistant rocks while the resistant rocks produce ridges that influence the direction of water flow. The pattern consists of short tributaries flowing into long main stem rivers in the main valleys. These alternating ridges and valleys are common in the "Valley and Ridge" province of the Appalachians in places like central Pennsylvania.

alpine glaciers

found in mountainous areas where the ice is channeled through pre-existing valleys.

Hygroscopic water

is a very thin layer of water molecules that becomes attracted to and attached very strongly to soil particles. Hygroscopic water is attached so strongly to soil particles that plant roots cannot extract it.

cirque

is an amphitheater-shaped landform that occupies the head of a valley. As several cirques erode toward the mountain top, they produce a pyramid-shaped peak called a horn

dissolved load

load is not sediment, but rather rock mass transported in dissolved form

radial pattern

looks like the spokes on a bicycle wheel. We find this type of pattern draining from conical landforms like volcanoes.

ablation zone

net loss of ice

How often do flows in rivers overtop their banks and spread over the floodplain?

once every 1-2 years

deranged pattern

pattern lacks organization, consisting of poorly integrated streams with an abundance of lakes and marshes. This pattern is common in young, recently glaciated landscapes. As time progresses, stream erosion will tend to drain the lakes and marshes and produce a more organized drainage network.

bedload

refers to the largest sediment particles that are too heavy to be suspended within the flow. Bed load slides, rolls, and is saltated (a hopping motion) along the bed of the channel

equilibrium line

the boundary between the zone of accumulation and the zone of ablation

floodplains

the flat area adjacent to channel built by river deposits An overbank flood occurs about once every 1-2 years. Therefore, the floodplain is also inundated about once every 1-2 years

till plains

the flat area after the glacier moves, trail of glacial till

meanders

the most common channel pattern. The bends apparently result from an inherent tendency for flowing water to follow a curved, meandering path. Whatever their origin, water flow through an individual meander bend causes a corkscrewing motion that is pushed towards the outside of the meander bend. This undercuts the outside channel bank, leading to collapse and erosion of the cut bank.

infiltration

the process of water entering the soil

driftless area

was never covered by glacial ice wisconsin

base flow

water supplied to streams by groundwater

accumulation zone

where there is a net gain of ice