Geography Exam 3
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Describe how snow transforms into glacial ice.
Heavy snow falls during winter
Snow does not completely melt during the summer– takes hundreds to thousands of years
snow accumulates annually in layers • equivalent to layers of sediment in sedimentary rock
Know how glaciers form
- 1: Snow falls, 80% air, new snow piles on top of old snow.
- 2. Snow compacts, melt and freezing cycles, becomes firm
- 3. Air is almost completely squeezed out, more than 40m deep, begins to flow
How glaciers change in size (glacial mass budget)
Inputs - Snowfall
Outputs - Melting, evaporation and sublimation
• Annual snow fall exceeds melting, evaporation and sublimation
• Accumulation of ice from snow fall
• Zone of accumulation
- • Higher temperatures down the valley
- • Melting and evaporation exceeds snowfall
- • Zone of ablation
- • The boundary between the zones of accumulation and ablation is called the equilibrium line– Inputs and outputs are in balance
Know the 2 ways that Glaciers can move
Plastic Flow: Glaciers flow under their own weight.
Basal Sliding - Pressure from weight of glacier melts small amount of water under the glacier
Cirque Glacier (Alpine)
Form in bowl-shaped depressions high on mountains
Feed into larger glaciers
Glacier flows in steep-sided valleys that were originally carved by streams
Glacier extends entirely out of the valley into the lowland in front of the mountain
Leaves narrow valley for flat lowlands so spreads out
Glaciers that terminate at the ocean or sea
- • Huge ice mass that covers a large part of a continent or large island – Also called ice sheets • Once covered much of North America and Europe
- • Now confined to Greenland and Antarctica
- • Several thousand meters thick
Explain how glaciers erode the landscape and the different landscape features formed by
- 1. Abrasion (like sandpaper) - Sand or fragments of bedrock frozen to the bottom of the glacier – Fragments grind down the underlying bedrock
- • Creates glacial striations– Scratches that indicate the direction of glacial movement
- 2. Plucking -
- • Glaciers loosen, pick up, and remove parts of larger blocks of rock
- • Rocks or boulders that are picked up are dropped later in random locations – Known as glacial erratics– E.g. Sioux Quartzite (bedrock from SW Minnesota) now found in Nebraska and Kansas
• Ridge-like feature that forms at the front, side, or in-between glaciers
• Forms only when a glacier is stationary for a while – Internal movement of the ice continually brings forth sediment for a ridge to grow
• Sediment is unsorted
Know the most recent periods of glaciation on Earth.
• PreIllinoisan– Numerous glacial advances and retreats that are difficult to separate so lumped together as PreIllinoisan
• Illinoisan– 300,000 years ago
• Wisconsin– 35,000 to 10,000 years ago – covered 30% of Earth’s land surface, vs. 11% today
Forms along the edge of a glacier • Most easily seen along the edge of alpine troughs
Form at the front of the ice
Mark the furthest advance of the glacier where it was stationary
• Form when retreat of ice is slow but steady (warm and melting)
•Irregular pattern of deposition
• Landscape is hummocky (small hills and depressions)
• Developed by a range of glacial processes • Composed of till
• Show the direction of ice flow
• Flat landscape created by deposition of sediments carried by glacial melt water flowing in front of the glacier
• Glacial streams are full of coarse sediment – braided streams
• Large blocks of ice melted and fell of the front of glaciers
• Ice buried by glacial outwash sediment as glacier retreats
• Ice melts and outwash sediments sink --> forms a lake – Lake will remain if it intersects the water table
Describe what soil is
• Uppermost layer of the Earth’s surface capable of supporting plants, formed from minerals (weathered rocks) and organic matter
4 main components of soil
1. Inorganic Material -Minerals that come from weathered rocks – Crystalline structures depending on the rocks they originated fro, Minerals contain different elements that are essential for plant growth – Released via weathering and absorbed by the plants.
2. Organic Matter
Formed from living and decayed organisms, accumulates in the upper part of the soil as humus.
Increases soil material because microbes decompose plant material – Release essential plant nutrients
Decays faster when there is oxygen present (aerobic decomposition), and slower when there is no oxygen because the soil is saturated (anaerobic decomposition)
- 3. Soil Water - Fill with water – At capacity = saturated– Drains to groundwater under gravity – Water drawn upwards via capillary action
- • Water held to soil pores due to surface tension
Describe how soil is formed over time
Organisms, relief, time, climate, parent material.
Four major processes that influence soil development
Additions - Organic matter, Precipitation Minerals and sediments solar radiation, O2 and CO2
Depletions - Sediment, Soil water, Organic matter and Soil minerals
- Transformations - Organic matter -> humus Minerals -> other minerals
- Minerals -> smaller sizes
- Soil particles clump together
What is a soil profile?
a vertical section of the soil from the ground surface downwards to where the soil meets the underlying rock.
what do the different soil horizons represent?
Distinct, genetic layers.
Soils of recent origin
• Contain no horizons except A horizon
• Reasons for lack of development – Climate is very dry – Parent material is quartz sand, which is very resistant to weathering – Parent material has been recently deposited, so little time for soil forming processes
• From Latin mollis, "sok”
• Soils of grassland ecosystems
- – Great Plains of the Midwestern U.S.
- – Broad region of Eurasia, including Russian steppe – Pampas of South America
- • Cooler climates
- • Clay-enriched B horizons (illuviation)
- • High concentra<ons of Al and Fe ions
- • Thinner A horizon than mollisols
- • Soils that are composed mainly of organic materials – at least 20-30% organic matter by weight and are more than 40 cm thick
- • Form in wet sites – Organic matter decomposes slower under water (anaerobic decomposition)
- - Very high clay content
- – Swell when they are wet and shrink when they are dry
- – Strong structure
- – Constant mixing of soil horizon when cracks form
- Occur in very cold climates—high latitudes or high elevations
- Contain permafrost within 2 m of surface and large quantities of organic carbon
- Low soil temperatures cause soil-forming processes such as decomposition of organic materials to proceed very slowly
- Poorly formed B horizon
What is the major soil order in the Midwest
and in Illinois? How has that impacted
land use in this region?
Mollisols; it has made the production of agriculture skyrocket.
Understand what controls the distribution of plants and animals on Earth
Tolerance to the environment - CAN it survive here?
Competition - WILL it survive here?
History / seed sources / migration
If out-competed… organism cannot survive to reproduction age or it cannot reproduce even if old enough
Main things animals compete for: food, shelter
Main things plants compete for: nutrients, water, light
Two types of Succession
Primary Succession:no soil (and hence, no previous plants either)
Secondary succession: after a disturbance(disturbance destroys previous plant community)(soil remains)
Understand pioneer communities and characteristics
Pioneer species = wind dispersed seeds
Characteristics: light, wind, soil, moisture, temperature, seeds. Replaced by other species.
Aspen: common tree species
- -net change in species number or type is minimal
- -diverse (many species)
- -seldom attained (takes too long), disturbance is the rule
- -Wind tolerance
- -Moisture needs
- -Temperature tolerance
- -How are seeds dispersed?
- Changes during succession
- -increasing numbers of plants that can tolerate -low light
- -more diversity
- -more layering/stratification
Biomes are the world's major communities, classified according to the predominant vegeta1on and characterized by adaptations of organisms to that particular environment.
How does climate influence plant type?
Temperature & Moisture.
Appears very dense from overhead
- –Relatively open and dark near forest floor
- –Only dense vegetation on the floor
- near rivers and on slopes because light can get in
- soils: red, nutrient-poor Oxisols
- -Most nutrients are tied up in biomass, not soils
- -Extremely rapid nutrient cycling
-too dry for forest
- -not a function of temperature
- -high annual moisture deficit combined with low actual evapotranspiration
- -There are many COLD deserts!
- -Most deserts are dominated by woody shrubs/scattered grasses
- -Temp of warmest 3 months averages less than 45 degrees F
- -Too cold for trees
- - lowest diversity:mosses, lichens, grasses, sedges dominate
- -low growth habit (already discussed)
- -can photosynthesize at -10C
- -seeds may take 2 years to produce (flower one year, produce seeds the next)
- -underground food storage
- -dark colors and pigmentation,raises temperature by absorption
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