Earth Science - Exam 4 - CJK

Define: Striations

Striations are fine, parallel marks on solid rock due to glacier movements. Rock pieces frozen into base of glacier act as sandpaper. The direction of striations indicate the direction of glacier movement. (Like taking sandpaper across a smooth finished surface)

Define talus:

Talus is the coarse rubble accumulating at the foot of a slope that is prone to rockfalls.

What is an Equilibrium line?

The equilibrium line is the line in a glacier indicating no net gain or loss. Above the line snow accumulates, below the line ice ablation occurs.

How can slope affect materials?

The steeper the slope, the greater the shearing stress, the greater the likelihood of slope failure.

Define Falls (In regards to land movement)

The term "Falls" refers to free-falling action in which moving material is not always in contact with the ground below. Rockfalls are the most common form. Falls usually occur in an area with a steep slope and loose rocks up high due to erosion and weathering.

What is a glacial terminal point?

The terminal point is the end of a glacier. Temperatures at the terminal end of a glacier are warmer because this is where the movement is and the altitude is lower.

What factors influence slope stability?

Things that may effect slope stability include: Weathering / fracturing Slow tectonic formation Moisture / fluid content Soil type Vegetation Earthquakes

What is glacial till?

Till is sediment deposited directly from melting ice of glacier. It is typically angular, poorly sorted material.

How does topography affect desert formation?

Topography: High mountain ranges along path of principal air currents between ocean and desert. Moisture-heavy air from ocean moves inland over mountains. The air cools at higher altitudes and looses its moisture. Dry air moves farther in land and down mountain side. Rain shadow is cast by mountains on inland areas.

What are possible causes of ice ages?

Two possible factors: Blocking of incoming solar radiation by something in atmosphere. May have sustained long periods of cooling. Variation in tilt of earth's axis, irregularity in earth's orbit. Distance between sun and earth not constant. Affects sunlight distribution, result in long-term cyclic variations.

What are ventifacts?

Ventifacts are exposed boulders that are planed off in direction of abrasion. Tall rocks may be undercut if wind velocity is slow and can't lift particles high off ground.

What is calving?

Calving occurs when a glacier encounters water. The advancing edge of the glacier flows over water and breaks up to form icebergs.

What are greenhouse gases (examples of gases)?

Carbon Dioxide (Co2) Methane (Ch4) Nitrous oxide (No2) CFC's plus others (these are the main ones)

What is the main gas associated with global warming?

Carbon Dioxide, however methane is much more dangerous. We don't generally worry about methane because we have a much higher quantity of Carbon Dioxide being added to the atmosphere.

What is the greenhouse effect?

Carbon dioxide molecules function like glass in a greenhouse. Light passes through, heats earth's surface. Carbon dioxide traps heat in atmosphere. Carbon based fuels contain and release much carbon dioxide. Greenhouse gases promote atmospheric warming. carbon dioxide amounts have increased 30% since industrial age - mid-19th century. Resulting in increase in global surface temperature of about 0.8c or 1.4f.

What is significant about clay in regards to soil composition?

Clay absorbs water easily, however clays fail easily under stress. Some clays expand when wet and contract when dry which destabilizes the slope.

What are the climatic conditions of a desert?

Dry: Less then 10cm of precipitation annually. Temperatures can vary, ice sheets can be classified as deserts.

How do dunes migrate?

Dune migration will occur if wind blows from predominantly a single direction. -Particles roll or move up shallower slope and pile up at the peak and slip down the steeper face (the slip face). -The slip face assumes the angle of repose. -Dune migrates slowly downwind. -Slanted crossbeds form by layers of sediments sliding down the slip face. -Problems - the migration will cover structures, forests, etc.. Planting vegetation may not work due to lack of hydration.

What is El Niño? (Be able to describe the phenomenon and its effects)

El Niño is the suppression of up welling of nutrient-rich deep waters of west coasts of north / south Americas and Africa. It may last for weeks or longer. Warm waters extend eastward to South America. Reduction in up welling can have devastating effect on commercial harvest. It is a cyclic event that occurs about every 4-7 years as part of El Niño-Southern Oscillation(Enso) This results in very heavy rainfalls, mudslides, and flooding in areas such as California. Normally you would expect cold water to come up to the surface of the ocean. El Niño stops that event. Both El Niño and La Niña are associated with changes in frequency, intensity, and paths of Pacific storms. They are associated with short-term droughts and floods and affect the timing/ intensity of India's monsoon season.

What is firn?

Firn is very thick, very dense ice associated with glaciers.

What are some possible consequences of mass movements?

Flooding can be triggered by mass movements. Landslides can dam up streams. Mass movements can result in extensive property damage.

Define flows:

Flows happen when material moves chaotically and in a disorganized mass. Particles within the mass mix much like a fluid. Flows could be comprised of soil, snow, pyroclastic flows, earth-flow (earth), mud-flow (soil saturated with water i.e. lahars)

What is frost heaving?

Frost heaving describes the separation of material due to the expansion of wet soil as it freezes. (Ice expands) The freezing moisture loosens and displaces soil making it more likely to slide next thaw.

What is glacial drift?

Glacier drift is deposition including both till and outwash.

How do glaciers move? (Be able to explain this process)

Glacier flow is plastic, different parts move at different rates. Movement is slow at the base of a glacier where it is in contact with and scrapes the valley walls. Movement higher in the glacier is faster. Fresh snow adds weight and pushes downhill. Overall glacial movement is slow and steady (a few tens of meters per year). Surges are possible (several tens of meters/day). Glaciers may also slide on melt water at base. There are primarily two ways in which glaciers may move. They can expand under their own weight, or slip due to a loss of friction between the glacier and the land under/around it. Additionally a glacier can advance and retreat in response to the melting and freezing.

What is glacier retreat?

Glacier retreat is the term describing the reduction of glacier size. It does not refer to the glacier moving backward, it refers to the size reducing.

Define Glaciers:

Glaciers are masses of ice that move over the land under its own weight due to gravity.

Where are glaciers found? Where do glaciers originate?

Glaciers are mostly found in mountains as snow patches that survived summer melting. Slopes facing poles are more protected from stronger sunlight (I.e. North slope in northern hemisphere). Gentle slopes allow snow to pile. Snow capped peaks are often glaciers.

How do glaciers affect surface topography?

Glaciers cause land erosion much like sandpaper moving across wood. Alpine glaciers cut their own valley (usually U-shaped)

What conditions must exists for a glacier to form? What are the requirements?

Glaciers form over a long period of time (not in one season) - climate must be cold enough for snow / ice year-round. They require certain latitude and altitude (I.e. may be in tropical areas at the appropriate altitude.) Glaciers require sufficient moisture in air for precipitation. The amount of winter snowfall must be more than summer melting.

What are some advantages and disadvantages of loess?

Good: Minerals in loess provide nutrients to plants in farmland. Good: Loess is porous and open in structure resulting in good moisture holding capability. Bad: Not suitable for foundation material. Bad: Subject to hydro-compaction - settles, cracks, denser when wet. Bad: Weight of large building can cause settling, collapse.

What part(s) of the U.S. are vulnerable to desertification?

In U.S. - already more than 1 million square acres of land in western U.S. has undergone severe desertification. Much of western half of country classified as semi-arid based on precipitation.

What is La Niña? (Be able to describe the phenomenon and its effects)

La Niña is the opposite of El Niño. Unusually cool waters are found off western Africa. This can trigger large-scale changes in evaporation and precipitation. Can alter wind-circulation patterns. Both El Niño and La Niña are associated with changes in frequency, intensity, and paths of Pacific storms. They are associated with short-term droughts and floods and affect the timing/ intensity of India's monsoon season.

What are landslides?

Landslide is a general term for the results of rapid mass movement.

What are landslide warning systems based on?

Landslide warning systems are based on relationships between rainfall intensity, storm duration, slope and soil characteristics (Slope angle, pore fluid pressure, shear strength).

What impacts can earthquakes have on slopes?

Landslides are a common consequence of an earthquake. Seismic waves passing through rock may stress and fracture it; reducing shear strength. The loss of shear strength may result in immediate movement.

What is loess?

Loess is wind-deposited sediments composed of fine particles, silts, etc. -Principal loess deposits in U.S. are in central part of country - concentrated around Mississippi River drainage basin. -Rivers drained meltwater from retreating ice sheets. -Glacial grinding produced sediment for loess

What are possible results of desertification?

Loss of native vegetation, seriously increased erosion, reduced crop yield.

What is mass wasting (Mass Movements)?

Mass wasting / movements occur when geological materials move downward from one place to another. The movements may be slow and subtle or sudden and devastating.

How can glaciers be artificially triggered to increase / decrease in size?

Methods include: -Cloud seeding to increase precipitation, increase water stored in glacier. -Dusting ice with dark material to increase melt

How does moisture/fluid impact slope stability?

Moisture may act as an adhesive, however too much may weaken stability by reducing friction and adding weight. Additionally the expansion and contraction of water through freezing and thawing can create cracks in material; this is known as frost wedging.

What are moraines?

Moraines are landfills made of till.

What is outwash?

Outwash is till moved and redeposited by meltwater. If till is picked up and moved it is considered outwashed.

How does vegetation influence slope stability?

Plant roots provide a strong interlocking network to stabilize materials and prevent flow. Vegetation removes moisture from the soil and may increase shear strength. On the other hand, plants add weight to the slope. Adding a large amount of weight to a slope with a limited root network can result in slope destabilization.

Define: plucking

Plucking is tearing away of small rock pieces frozen to the glacier.

How can individuals assess and recognize the risk of mass movement hazards? What should one look for?

Potential warnings include: -Past history of movement -Areas bare of vegetation -Past history of snow avalanches and volcanic activity -Aerial photography or quality topo maps -Tilting tree trunks is a sign of soil creeping. -Cracks in driveways, foundations, walls, etc. -Doors, windows that don't close properly

What are possible ways to prevent/reduce risk of mass movements? Be able to explain the methods.

Prevention methods include: -Reduce the slope angle by placing additional supporting material at foot of slope to prevent slide/flow. Reduce load by removing higher material. Use a combination of methods. -Retention structures: Fast-growing plants with extensive root systems. Retaining walls to hold slope in place (Most successful with low, thick walls at toe of coherent slide.) -Fluid removal: Decrease water content or pore pressure of rock/soil by covering surface with impermeable material, divert surface runoff, and/or use subsurface drainage pipelines to carry water from slope. -Vertical piles into foot of shallow slide (Limited to areas where slide is fairly solid and low angle.) -Use of rock bolts to stabilize rock slopes(Anchor rock slide with giant steel bolts driven into more stable rocks) -Bridge structures allow material to flow over structure.

Where is loess principally found in the U.S.?

Principal loess deposits in U.S. are in central part of country - concentrated around Mississippi River drainage basin.

What are quick clays?

Quick clays are a type of sediment formed from glacial rock flour deposited in a marine setting.

What is the global impact of desertification?

Reduces arable land available for food production. Areas already vulnerable to desertification. Close to 40$ of world's land surface is "drylands" and does not include true deserts. In near future, 1/3 of once-arable land may become useless for food production. Example - Ethiopia - long drought combined with overuse of land by humans.

What is rock flour?

Rock flour is fine sediment of pulverized rock produced by glacial erosion.

Define rock slides:

Rock slides are typically movement along a bedding plane between successive layers of sedimentary rocks.

What is scarp?

Scarp is the newly exposed land after a mass movement.

What is shear strength?

Shear strength is the ability of a material to resist shearing stress. When shearing stress exceeds frictional resistance sliding occurs.

What is shearing stress?

Shearing stress is stress that tends to cause different parts of an object to slide past each other across a plane. Stress tends to pull materials down slope.

What is the current trend seen in glacier movement?

Size and movement of glaciers vary over time. However, currently the our glaciers are generally retreating a lot more then they are advancing. (Note: Retreating does not mean it is moving back. It means that it is melting faster then it is accumulating.)

Define slides:

Slides occur when material moves as a cohesive unit downward along a clearly defined surface. Contact is kept with the ground during a slide.

Define slumps:

Slump refers to material moving down slope accompanied by rotation (soil or rocks). A land slide comes straight down. A slump rotates, falling over, on itself. A rock slide that doesn't move far could also be considered a slump. A slump typically does not move very far.

How does snow transform into ice?

Snow accumulates during cold periods. Overlying snow will pack the ice (and underlying snow) tighter and thicker pushing out most of the air. Packing causes the ice to recrystallize into a denser ice called firn.

What are potential problems associated with global warming due to greenhouse effect?

-Agriculture - marginal areas may become unusable with even slight temperature increases. -Warmer Temps resulting in faster glacial melting leading to more changes in global weather patterns. Summer soil-moisture content could drop drastically. -Increased sea level from glacial melt waters. If all ice melts then increase of nearly 250 feet. -Co2 levels could double by middle of next century. Further increasing impacts. (Temps rise 7.14f. Increase of sea level by 3-6 meters.)

What lands are at risk of desertification?

-Arid - annual rainfall less than 10 inches. -Semi-Arid -annual rainfall less then 10-20 inches. -Extremely arid lands - may have at least 12 consecutive months without rainfall.

What kinds of evidence can scientists use to determine past climates?

-Geologic record - sedimentary rock - Example Nebraska sand hills - remnants of arid sand sea from 18,000 years ago during drier conditions. Now more precipitation hills covered by vegetation. -Coal deposits indicate previous wet, warm conditions (swamps) -Evidence of glacial deposits in now-tropical regions. -Marine sediments indicate water-temperature variations. -Oxygen isotope variations in geological materials -Ice cores from continental glaciers

What types of things are being observed today that provide evidence of global warming?

-Majority of alpine glaciers are retreating. -Sea ice is decreasing in extent and thickness. -Greenland ice cap thinning at more than 3 feet per year. -Average global temps are warming. -Permafrost is being lost due to annual thaw penetrating deeper and deeper into the ground.

What conditions cause desert formation?

-Moderately high surface temperatures allowing rapid evaporation of surface water. Warm air holds more moisture then cool air. Topography: High mountain ranges along path of principal air currents between ocean and desert. Moisture-heavy air from ocean moves inland over mountains. The air cools at higher altitudes and looses its moisture. Dry air moves farther in land and down mountain side. Rain shadow is cast by mountains on inland areas. Distance from ocean: Oceans are a major source of air moisture. The longer the air mass moves over dry land, the greater the chance it loses moisture. Contributes to desert formation in continental interiors. (Coastal oceans may occur due to hot land and cool ocean)

What is the definition of a desert?

A Desert is a region with limited precipitation, animals, and vegetation. Deserts are a type of ecosystem. A Desert may not be hot or dry - ice sheets are classified as deserts also. A Desert is defined as an area with less then 10 cm precipitation annually. Temperatures may very regionally.

What are dunes and how do they form?

A Dune is where sediment has been deposited by the wind. -Low ridge or mound - usually composed of sand. -Formed where winds slow down and drop sediments. -Can be large in size - may consist of other materials. -Orientation of dune indicates prevailing wind direction. (Shallower sloping side faces upwind.)

Define: horns

A Horn is erosion from several glaciers around a single peak.

Define: cirques

A cirque is a bowl-shaped depression carved by a glacier.

What is a rain shadow?

A rain shadow is a dry area on the inland side of a mountain range. It is caused because air from the ocean cools as it increases altitude resulting in the dumping of water on the ocean side of the mountain.

What are sensitive clays?

A sensitive clay is a type of quick clay that can change from a relatively stiff condition to a liquid condition when disturbed. They form when rock flour is deposited into a marine environment and sediment is uplifted by plate tectonics. NaCL acts as glue to hold clay particles together. Fresh water infiltrates the clay and washes out the salts resulting in a honeycomb like structure. Seismic vibrations can break apart the structure, reducing the strength by as much as 20-30 times, creating a quicksand-like material that is prone to sliding.

What is ablation?

Ablation is the loss of glacier ice by melting or evaporation.

Explain how abrasion can occur from wind erosion?

Abrasion from air is the wearing away of a solid object by impact of particles carried in the wind. It's much like sandblasting. It is more effective on sediments than solids and in areas where sediment is exposed.

Define: abrasion

Abrasion is the erosion by scraping of ice or sediment underneath. It is more of a general roughing up of the surface.

What is an alpine glacier?

Alpine glaciers are also known as mountain or valley glaciers. They occur at high altitude (cooler temperatures). Valleys in mountainous terrain, include most of today's glaciers.

Which is more numerous: alpine glaciers or continental glaciers?

Alpine glaciers are more numerous.

Define: Arête

An Arete is a ridge left between two glaciers moving side by side.

What is the difference between an end moraine and terminal moraine?

An end moraine is curving ridge of till that was pushed ahead of glacier. It accumulated at glacier's end by advances and retreats. A terminal moraine is the farthest moraine deposit. It marks the point at which the glacier began retreating. As a glacier moves you will find a series of piles of sill deposition. Each individual pile is called a end moraine. The last pile, the pile furthest away, is the terminal moraine.

What is angle of repose?

Angle of repose is the maximum slope angle at which a material is stable. The angle varies with the material type: Smooth, rounded particles result in low-angle slopes. Rough, sticky, irregular material results in higher angle slope (i.e. steeper) without becoming unstable. Coarse fragments usually maintain steeper slope than fine fragments. Generally the finer the material the lower the angle of repose. (and vice versa, the larger the material the higher the angle of repose) The slope a material forms when you dump it is its natural angle of repose. A material, given time, will tend to transform back to its natural angle of repose.

How do glaciers provide water for populations?

Approximately 75% of fresh water is stored as glacial ice. In areas of large numerous glaciers meltwater provides principal source of summer stream flow.

Define avalanches:

Avalanches or debris flow involve a wide range of material involvement: trees, soil, and rock.

What are some ways in which human activities can impact mass movement negatively?

Clearing of stabilization vegetation by clear-cutting and burning. Over-steepening slopes due to construction Removal of material at bottom ends of layers can leave large rock masses without support and held by friction alone. Building house above naturally unstable or artificially steepened slope adds weight and increases shear stress. Overuse of water - watering yards, septic systems, etc.

What is the difference between an alpine glacier and a continental glacier?

Continental Glaciers are larger then alpine, but rarer. There is more total ice in continental glaciers then in alpine glaciers.

Which has more ice: alpine glaciers or continental glaciers?

Continental Glaciers have more total ice.

What is a continental glacier?

Continental glaciers also known as ice caps or ice sheets. They occur near the poles (over land); they are larger and rarer. May be as thick as 1km or more. Fewer in number but contains more total ice than alpine. Two principal continental glaciers - Greenland, Antarctic.

What is creep?

Creep is slow short distance movement of land.

What is deflation?

Deflation is wholesale removal of loose sediment by wind.

What is desert pavement?

Desert pavement is substrate produced by combined effects of wind erosion and overland surface-water runoff. -Large rocks are exposed by selective removal of fine sediments. -Finer materials remain below and are protected. -Stable structure unless the larger rocks are disturbed.

What is desertification and why is it of interest and importance?

Desertification is the process by which marginally habitable arid lands are converted to desert. The process is accelerated by human activities.

What are causes of desertification?

Desertification usually involves severe disturbance of limited vegetation. - Farming - If you remove native vegetation and put in non-native plants you will increase the chance of desertification. If crops fail or land remains barren for period of time: Erosion, loss of soil fertility, and loss of soil structural quality. Soil bakes, hardens, no roots to loosen soil. Increased runoff, decreased infiltration, decreased soil moisture and groundwater. -Livestock - Vegetation may be reduced or stunted during drier periods. Livestock strip vegetation for food and moisture. Increases grazing pressure on land. Soil is stripped bare. - Natural drought cycles - Not much impact in absence of human land uses. In absence of humans, systems can recover. Human activities combined with drought can cause permanent damage.