Earth Science, Tarbuck Chapter 10 Flashcards
What is a glacier
thick ice mass that forms over hundreds
or thousands of years.
What are valley/Alpine glaciers
relatively small glaciers that exist in lofty mountain areas, where they usually follow valleys originally occupied by streams
When was the Last Glacial Maximum
Around 11,000 years ago the wisconsin glaciation ended
What is the North Pole Covered in
Sea Ice
What are the 2 main ways a glacier moves
Plastic flow and Basal Slipping
What is Plastic Flow in a glacier
movement within the ice as if there is enough overlaying pressure, it will behave like a plastic material
How many meters of ice is required for enough pressure in a glacier for plastic flow to begin
around 50 meters
What is the top 50 meters of glacier called
Zone of Fracture
Why is the top 50 meters of a glacier called the zone of fracture
There is not enough ice for the top 50 meters to be ductile
What are crevasses in Glaciers
cracks on the glacier caused by tension
What is the deepest a crevasse in a glacier can be
50 meters
What is the zone of accumulation in a glacier
The zone where Snow accumulation and ice formation
occur
What is the Equilibrium Line
the elevation at which the accumulation and wasting
of glacial ice is equal
What is the zone of ablation/wasting in a glacier
Zone where there is a net loss in Ice
2 Ways that Glaciers erode rock
Plucking and Abrasion
Describe Plucking Erosion
meltwater penetrates the cracks and joints
along the rock floor of the glacier and freezes, which pries the rock loose
Describe Abrasion Erosion
ice and its load of rock fragments slide over bedrock,
they function like sandpaper, smoothing and polishing
the surface below.
Pulverized rock formed by Abrasion Erosion is called
Rock Flour
What are Glacial Striations
long scratches and grooves formed by Abrasion Erosion if the glacier contains lots of large rock fragments
If a glacier does not have large rock fragments on the bottom and performs abrasion erosion, what happens to the bedrock below
Bedrock below becomes highly polished
What is the shape of the valley after a glacier erodes through it
U shaped
What are Main Glaciers also called
Trunk glaciers
The amount of glacial Erosion depends on what
Thickness of Glacier
How do hanging valleys form
Trunk glaciers, or main glaciers, cut deeper into valleys than their tributaries do. This causes the valleys of the tributaries to be hanging when the glaciers retreat
What is a cirque
bowl-shaped depressions with walls on three sides and a open side on the down valley. They are formed at the head of the glacial valley and is one of the alpine glaciers defining features
Why is the cirque the focal point of a glaciers growth
The cirque is the area of accumulation and ice formation
What is a Tarn
Small lake in the cirque after glacier retreats
What are Aretes
knife-edged ridges caused by erosion of 2 or more glaciers
Why is Bedrock Often not exposed in areas where glaciers once were
Deposition of Glacial Sediment covers up bedrock.
What is glacial Drift
Sediment Originating from glaciers
2 types of Glacial Drift and what each type is
Till, material Deposited directly from the glacier, and Stratified Drift, which is sediment deposited from glacial meltwater
Glacial Till sediment is often
Polished and Scratched due to movement of glacier
What are Glacial Erratics
Boulders found in till or lying on the surface and having different rock composition than bedrock
Difference between Stratified Drift and Glacial Till
Stratified Drift is sorted as meltwater transports the sediment
What are Moraines
Ridges or Layers of Till
What are Lateral Moraines
As a glacier moves forward, it picks up sediment on its sides, causing it to form ridge-like deposits on the sides of the glacier
What are medial moraines
Medial Moraines are Ridge-like Moraines formed when 2 Lateral Moraines of 2 different Glaciers merge as the glaciers form 1 ice stream
What is an End Moraine
Moraine formed at the terminus of the glacier as the glacier pushes forward it accumulates lots of till.
What are Ground Moraines
Gently Rolling layer of till deposited behind the end moraine when the glacier starts retreating
Effect of Ground Moraines on Surrounding topography
Fills in Low spots and Clogs old streams channels
What are terminal end moraines
End moraines that mark the glaciers farthest extent
What are recessional end moraines
When ice front occasionally stabilizes, a new end moraine is made.
What are Outwash plains
Area of Flat land in front of a glacier that consists of many braided streams
What is a Valley Train
Outwash Confined within a valley
What are Kettles
Basins or Depressions found near glaciers that form when blocks of stagnant ice become buried in glacial drift, causing a depression to form after melting
What are Drumlins
Asymmetrical Hills composed of till, where the steep side faces the direction the glacier came from and the gentle side faces the direction the Glacier is moving towards
Do drumlins form in groups or are they found individually
Groups often called drumlin fields
What are Eskers
Ridges composed of sand and gravel formed when streams flowing in tunnels beneath the ice deposit their sediment near the terminus of the glacier
What are Kames
Steep-Sided hills formed of sand and gravel. Like eskers they form due to deposits of streams flowing in tunnels beneath the ice near the terminus of the glacier
What effect do glaciers have on Landscape and Sealevel
Areas covered by glaciers often are in lower regions due to the overburdening effect of the glacier. When a glacier retreats this causes the area covered to isostatically adjust and spring upwards.
Glaciers hold lots of water in them, when they retreat, that water is released and in turn causes an increase in sea level
How can Ice sheets and alpine glaciers act as dams
They can trap glacial meltwater and block the flow of rivers
What are Proglacial Lakes
Lakes that are formed due to glacial blockage just beyond the outer limits of a glacier or ice sheet
What are Pluvial Lakes
body of water that accumulated in a basin due to cooler and wetter climates
Glacial and Interglacial Cycles occur once every how many years
100,000 years
The amount of Glacial Ice in the Northern Hemisphere is about ______ of that in the Southern Hemisphere
Twice
Most of the major glacial episodes occurred during which period of time
Quaternary
What is tillite
Sedimentary Rock formed of Till
How do Plate Tectonics connect to ice ages
When plate tectonics move landmasses to polar places, an ice age is more likely to occur.
What are the 3 types of milankovitch cycles
Obliquity, Eccentricity, and Precession
What is Obliquity Milankovitch Cycles
Changes in the angle that Earth’s axis makes with the plane of its orbit
What is Eccentricity Milankovitch Cycles
variations in Shape of Earth’s orbit around the sun
What is Precession Milankovitch Cycles
Wobbling of Earth’s Axis
Eccentricity Milankovitch Cycle lasts about how many years
100,000 years per cycle
Obliquity Milankovitch Cycle Lasts about how many years
41,000 years per cycle
Precession Milankovitch Cycle lasts about many years
26,000 years per cycle
What are the 2 different types of Dry regions
Desert(arid) and Steppe(Semi Arid)
Where do most Dry regions form
Subtropics and Areas away from the Ocean
The lack of water in desert regions affects chemical weathering how
reduces efficiency of chemical weathering, thus mechanical weathering dominates in dry regions
How are floods different in desert regions compared to humid regions
Floods happen very quickly and subside very quickly due to low vegetation and high runoff levels
Why are desert streams often small and not last until the sea.
Water table is so low that the streams in deserts cannot pull water from them.
role of water as an erosional agent in deserts
Water is the main erosional agent in deserts despite their low quantity
Wind is mostly not an erosional agent it is mostly a
transportation and deposition of sediment
Dry regions typically lack permanent streams and often
have _______________
Interior Drainage
What is a Bajada
Combination of many alluvial fans that form an apron like blanket of sediment
What are Playa Lakes
Lakes that often do not last a long period of time
What is Deflation erosion by wind
lifting and removal of loose material
Wind can only suspend _______ particles
Fine
What is a blowout dunes
sandy depression caused by deflation wind erosion
What is sandy pavement
Layer of Coarse pebbles and cobbles too large for wind to move
2 types of wind deposits
Loess and Dunes
What are Loess Deposits
Extensive Blankets of Silt
What are Dune Deposits
mounds and ridges of sand from the
wind’s bed load
How are Loess Deposits Created
Dust storms deposited material over thousands of
years
How are Dune Deposits created
Mounds or Ridges Formed by wind dropping sediment in place as energy decreases after air meets a object
How is Cross Bedding Created
layers form that are inclined in the direction the wind is blowing.
Which side of the dune is steep
leeward, or sheltered side
Which side of the dune is gentle
Windward side
The leeward side of the dune can also be called what
Slip Face
What is saltation
When wind cannot pick up the coarser sediments, it picks them up and rolls them on the ground as bed load
Angle of repose for sand
34 degrees
Isolated Crescent shaped dunes
Barchan Dunes
series of long ridges that are separated by troughs dunes
Transverse Dunes
dunes with a mix between isolated barchans and
extensive waves of transverse dunes.
Barchanoid Dunes
long ridges of sand that form parallel to the prevailing wind
Longitudinal dunes
vegetation partially covers the sand. The shape of these dunes
resembles the shape of barchans except that their tips
point into the wind rather than downwind
Parabolic Dunes
isolated hills of sand that exhibit a complex form
Star Dunes
