Ch 19 Flashcards
-7% of the worlds erosion/ transportation of rock debris by glaciers.
-glaciation extent in passed was about 1/3 and now 1/10
-moving ice grids away anything in its way. Soil carried away
-bedrock polished/scraped:gouged/plucked/
abraded.
Impact of glaciers on landscape
- glacial topography/meltwater BASIS for many of the worlds lakes and ride channels.
- glaciers sculpted the alpine vistas(high glacier mountains) at heads of valleys.
- glacial deposits are the basis parent material for soils.
- glaciers cover sizable areas of earths land surface.
- deposition by ice sheets. Nice in kettle- sometimes potential lakes.
Direct impacts of glaciers
Glaciers in mountainous areas
Continental ice sheets.
Largest glacial ice today and types of glaciers
Antarctica S
Greenland N
-continental ice sheets.
Types of glaciers
Continental ice sheets
Mountain glaciers
Highland ice fields >outlets are valley glaciers.
Alpine glaciers-high in mountains
Cirque glaciers-very small alpines
Mountain glaciers
Long tongues of ice extend between rimming hills to the sea
Huge floating ice mass.
Outlet glaciers
Iceberg
May begin To develop if in a net to net year accumulation of snow in winter is greater than the amount of melting snow in summer. Each yr weighs down old snow and turns into ice. Ice moves to the pull f gravity eventually. Depends on accumulation>addition ice snow & ablation. >wasting ice melting and sublimation.
Glacial formation and movement
Snow Is changed to ice by “” and “”
Following a sequence from “” to granular snow to “” to glacial ice. “” happens by overlying newer snow on old snow.
Compression
Coalescence
Snowflakes
Neve
GLACIAL MOVEMENT
The Ice below surface of glacier (under confining pressure) “” but doesn’t break. Melting aids in movement as “” layer for sliding. Basal slip is an entire mass that slides over its bed on “” film of water & molds itself to the shape of the terrain it “”. Gravity flow, is always going “”
Deforms Slippery Lubricated Rides Forward
This erodes the landscape with IDE wedging, and freezing/thawing rock. The lower most ice melts w/friction against bedrock. Layer of water reduces “”. Water referees around rocky protrusions , exerts force as it is pushed by ice “” it. Rock particle are grasped as meltwater freezes in bedrock joints and fractures. Does wedging further loosens rock. As ice moves particles. And are plucked out while dragged along. This “” the underlying surface
Glacial plucking
Pressure
Behind it
Roughens
Bedrock is worn down by rock debris that’s dragged along in moving ice. Only “” surfaces when bedrock is of highly resistant material. This digs striations (in resistant) and “” in less resistant.
Glacial abrasion
Polished
Grooves
- bottom load transport-plucked/abraded debris.
- top load-(alpine glaciers only)
- rocks fall down high valley slopes onto ice.
- bulldozing- advancing glaciers (push) material along their front edges.
Transportation by glaciers
- All material moved and or deposited by glaciers “”
- ”” collection of debris of all sizes. Boulders to glacial flour(finely ground rock)
Two types of what?
Drift
Heterogenous
Transportation by glaciers
Rock debris deposit mites by moving/Melton ice -in sorted glimmer action of fragmented rock material.
Till
Outsized boulders by deposited retreating glaciers.
Glacial erratics
Deposited landforms composed entirely or largely of till. Lengthier than wider.
Moraines
3 moraines associated with continental ice sheets or mountain glaciers
Terminal
Recessional
Ground
Ridge full of till, marks the outermost limit of glacial advance (concave arc) -bulges outward in direction of ice movement.
Terminal moraine
Behind the terminal, develops glacier recedes. Ridges that mark the position where ice front was temporarily stabilized during the final retreat of the glacier. (Concave arc) Bulge outward in direction if ice movement.
Recessional moraine
Formed when large quantities if till are laid down from underneath the glacier rather than its edge. Gently rolling plains across landscape. May be shallow or deep. & consist of low knolls and shallow kettles.
Ground Moraine
Form when large blocks of ice left by A retreating glacier become surrounded or covered by glacial drift. After ice block melts. Moraines surface collapses and leaves irregular depression.
Kettles
Feature deposited by ice sheets, low elongated hill-“”- much smaller than moraines w/similar in sorted till. Origins of ice readvance onto area of previous glacial deposition.
Drumlin
Less common than outwash plains, more conspicuous long sinuous ridges I stratified drift. Glacial fluvial gravel & great deal of debris. Debris exposed when ice melts.
Eskers
erosion dominates upper portion of valley. Alpine glaciers/highland ice fields remodel the peaks and ridges and transform valleys
Erosion by mountain glaciers
Deposition by mountain glaciers
Moraines (principal features)
Well defined ridges of un sorted debris built up along the sides of alley glaciers. Can become medial moraine
Lateral moraines
Explanation must have four things
- Accumulation of ice masses in both hemispheres- w/I uniformity
- Concurrent development of Pluvial conditions in dry lands
- Multiple cycles of ice advance and retreat
- Eventual total de glaciation of glaciers
Causes of the Pleistocene
Variability in solar output (energy form sun changing)
Variation in amount of CO2(more heat)
Changing continent configuration of ocean gains and ocean circulation patterns
Change in circulation due to
increased elevations of continental mass after a period of tectonic upheaval.
Reductions in isolation due to volcanic eruptions
Other factors can feed to the collapse
