Glaciers Flashcards
Compare a glacier to an ice age
Glacier is a mass of slowly moving ice
Ice age is a period of time during which glaciers existed
How many ice ages were there? When was the most recent ice age?
Evidence for 4 ice ages; the most recent was about 10,000 years ago
how is a glacier formed?
- in colder regions of the Earth, snow that falls during the winter does not melt during summer
- Collected snow becomes deeper over time and lower layers are compressed by weight of upper layers
- compression causes the ice to melt; it flows downhill and refreezes, forming roughly textured ice (glacier ice)
How does a glacier move?
Pressure of the top layer of ice causes lower layers of snow to ice and melt. These layers lubricate the base and extend the area of the glacier. Gravity makes the glacier flow downhill
2 main types of glaciers
Alpine/mountain
Continental
Alpine Glacier
Formed in mountain valleys; small V-shaped streams erode valleys into a U-shaped glacier valley (found in the Alps and Rocky Mtns)
Continental Glacier
Covers large areas of land; made of huge ice sheets
Ex: Greenland, Artarctica, northern-N. America during Pleistocene era
Horn
Sharp edged, pyramid-shaped mountain peak present in areas where there are many alpine glaciers (Matternhorn in the Alps)
Cirque
Circular scoop high in a mountain area formed by erosion by frost; usually where alpine glaciers begin. Cirques on several sides of the mountain create horns
Moraine
Mass of rocks that are collected by glaciers as they move
3 basic types of moraine
ground
lateral
medial
Lateral Moraine
Material along valley walls; found on the side of a glacier
Medial Moraine
It is formed when two glaciers join; the lateral moraines of both glaciers collect in the center of the new one
Ground moraine
Rocks at the bottom of a glacier; these rocks cut deep grooves as they are dragged along the bedrock
Terminal moraine
A long ridge formed when rock fragments collect as the front of the glacier melts; they can be hundreds of feet high, and miles long and wide (ie Long Island has two large and long terminal moraines)
Outwash plain
Meltwater carries sand and other fine particles away from the front of a glacier. As it is deposited it forms an outwash plain that can have a several mile radius (ie southern shore of Long Island)
Erratic
Lg. boulder deposited by a glacier far from its place of origin
Drumlin
Small oval hill formed under a glacier as it moves (like Bunker hill, Boston)
Kettle hole
Glacier melts leaving a block of ice surrounded by moraine. There is a hole in the ground when the ice melts
Kettle lake
A lake formed when a kettle hole created by a glacier fills with water
Glacial lake
Glacial moraine builds up in a valley and forms a natural dam as it blocks the flow of water. Lakes are formed.
Ex: Finger Lakes, NY
Tarn
A small lake occupying a rock basin in a cirque; created by a glacier
How does wind erode and change the land?
If the surface of land is loose (sand, loose soil, silt, etc.) the action of wind will move it from one location to another
Wind abrasion
When strong winds pick up sand, the sand abrades and erodes surfaces it comes in contact with
Sand dune
Sandhill formed when wind carrying sand slows down due to obstruction. Sand falls and collects near obstruction and over time may form a large hill (like dunes on Cape Cod, White Sands, Sahara Desert)
Loess
A loamy deposit formed by wind, usually yellowish and calcareous, common in the MI Valley and in Europe and Asia; good for growing crops. Ex: topsoil in Missouri and other Midwestern states
Subduction
Type of plate movement where one plate dives down into the mantle beneath the more buoyant plate
