Glaciers Moving Ice

Formation of Glaciers A glacier is defined as a mass of moving ice. A glacier is defined as a mass of moving ice. There are several steps to their formation. There are several steps to their formation. The first step is for snow to accumulate above the snowline. A snowline is simply the elevation at which snow and ice will remain throughout the year. The first step is for snow to accumulate above the snowline. A snowline is simply the elevation at which snow and ice will remain throughout the year.

Snow line>

Formation of Glaciers (cont.) The second step is a snowfield must form. A snowfield is a motionless mass of permanent snow and ice. The second step is a snowfield must form. A snowfield is a motionless mass of permanent snow and ice. Low temperatures allow snow to accumulate year after year. As the snow partially melts and refreezes it changes into small grains of ice. This ice is referred to as a firn. Low temperatures allow snow to accumulate year after year. As the snow partially melts and refreezes it changes into small grains of ice. This ice is referred to as a firn.

Snowfield Snowfield

Formation of Glaciers (cont.) Fourth, in the deeper layers of the firn, the pressure becomes so great that the ice flattens out as air is squeezed out. The firn loses it’s white color and becomes a steel-blue. Fourth, in the deeper layers of the firn, the pressure becomes so great that the ice flattens out as air is squeezed out. The firn loses it’s white color and becomes a steel-blue. When the snow and ice become so thick that gravity begins to pull it downward, it is called a glacier. When the snow and ice become so thick that gravity begins to pull it downward, it is called a glacier.

Firn Firn

Types of Glaciers There are 2 main types of glaciers. You can tell them apart by their size and location. There are 2 main types of glaciers. You can tell them apart by their size and location. A VALLEY GLACIER, is formed in a mountainous area. As ice moves down a valley, it produces a long, narrow, wedge shaped mass. A VALLEY GLACIER, is formed in a mountainous area. As ice moves down a valley, it produces a long, narrow, wedge shaped mass.

Types of Glaciers (cont.) The second type of glacier is called a CONTINENTAL ICE SHEET. These glaciers cover large areas of land and are found only in Greenland and Antarctica. The second type of glacier is called a CONTINENTAL ICE SHEET. These glaciers cover large areas of land and are found only in Greenland and Antarctica.

Valley glacier Valley glacier

Continental Glacier

Movement of Glaciers A glacier can be compared to a river. They are similar because both move downward due to gravity. That is where the similarities end however. A glacier can be compared to a river. They are similar because both move downward due to gravity. That is where the similarities end however. Glaciers cannot move rapidly. The average speed that a glacier moves is 100 meters per year. Glaciers cannot move rapidly. The average speed that a glacier moves is 100 meters per year. Glaciers also cannot flow easily around a barrier. Glaciers also cannot flow easily around a barrier. Scientists who have studied glaciers agree that they move by two basic processes. Scientists who have studied glaciers agree that they move by two basic processes.

Movement of Glaciers (cont.) BASAL SLIP occurs when the weight of the glacier causes the ice that touches the ground to melt. The water acts as a slide for the glacier to move on. BASAL SLIP occurs when the weight of the glacier causes the ice that touches the ground to melt. The water acts as a slide for the glacier to move on. This also allows the glacier to work its way over small objects in it’s path by melting and then re-freezing. This also allows the glacier to work its way over small objects in it’s path by melting and then re-freezing.

Movement of Glaciers (cont.) INTERNAL PLASTIC FLOW occurs when solid ice crystals slip over one another, causing slow forward movement. INTERNAL PLASTIC FLOW occurs when solid ice crystals slip over one another, causing slow forward movement. This type of movement allows different parts of the glacier to move at variable speeds. This type of movement allows different parts of the glacier to move at variable speeds. Ice near the surface and center moves faster than on the sides of the glacier. Scientists have learned that the slope, thickness, and temperature of the ice determine the speed at which the glacier moves. Ice near the surface and center moves faster than on the sides of the glacier. Scientists have learned that the slope, thickness, and temperature of the ice determine the speed at which the glacier moves.

Basal slip Basal slip

Glacier Features CREVASSES are large cracks in the brittle surface of the glacier. Crevasses can be more than 30 meters deep. Because a thin layer of snow can hide crevasses, traveling over them can be very dangerous. CREVASSES are large cracks in the brittle surface of the glacier. Crevasses can be more than 30 meters deep. Because a thin layer of snow can hide crevasses, traveling over them can be very dangerous. Glaciers that have moved out over the ocean are called ice shelves. The largest known ice shelf covers an area the size of Texas. Glaciers that have moved out over the ocean are called ice shelves. The largest known ice shelf covers an area the size of Texas. The oceans tides break off pieces of the ice shelf, which then float out into the ocean. These are called icebergs. Most of an iceberg is located underneath the surface of the ocean, so they can be dangerous to ships. The oceans tides break off pieces of the ice shelf, which then float out into the ocean. These are called icebergs. Most of an iceberg is located underneath the surface of the ocean, so they can be dangerous to ships.

Questions to answer How many steps are in creating a glacier? How many steps are in creating a glacier?4 When the snow and ice become so thick that gravity begins to pull it downward, it is called a _______ When the snow and ice become so thick that gravity begins to pull it downward, it is called a _______ What are the two types of glaciers? What are the two types of glaciers? What 2 water features are similar because both move downward due to gravity? What 2 water features are similar because both move downward due to gravity? 1 23 glacier Continental and Valley Rivers and glaciers

Questions to answer cont.. There are_______ processes when talking about glacial movement. There are_______ processes when talking about glacial movement. 2 Ice near the ________ and _______ moves faster than on the _______ of the glacier. Ice near the ________ and _______ moves faster than on the _______ of the glacier. Glaciers move from the _______ because _____ acts like a _______ Glaciers move from the _______ because _____ acts like a _______ What are three features a glacier makes? What are three features a glacier makes? SurfaceCenter Sides Water Lubricant Bottom Crevasses, icebergs, ice shelves

15.2 Landforms created by glaciers Cirque- bowl shaped depression Cirque- bowl shaped depression Arêtes- saw-toothed ridges Arêtes- saw-toothed ridges Horn- Pyramid like peak Horn- Pyramid like peak Hanging valley- ice melts a smaller tributary of glacial ice above the main valley floor Hanging valley- ice melts a smaller tributary of glacial ice above the main valley floor

This is the bottom of a glacier This is the bottom of a glacier As you can see most of the “damage” is caused by the base or bottom of the glacier As you can see most of the “damage” is caused by the base or bottom of the glacier

Till- unsorted deposits of rock material Till- unsorted deposits of rock material Stratified drift- sorted and deposited in layers Stratified drift- sorted and deposited in layers Melt water- streams of water that carry the stratified drift. Melt water- streams of water that carry the stratified drift. Erratics- Large boulders Erratics- Large boulders

Melt water Stratified Till Erratics

Moraines Lateral- on the SIDES of the glacier Lateral- on the SIDES of the glacier Medial- in the middle of the glacier Medial- in the middle of the glacier Ground- beneath the glacier Ground- beneath the glacier End/Terminal- the snout or “front” of the melting ice End/Terminal- the snout or “front” of the melting ice Outwash- stratified drift and melt water streams Outwash- stratified drift and melt water streams Eskers- are the long winding ridges of gravel left behind Eskers- are the long winding ridges of gravel left behind

Glacial lakes Our own great lakes was once at the bottom of a huge glacier. Our own great lakes was once at the bottom of a huge glacier. It took 10,000 years to develop our great lakes It took 10,000 years to develop our great lakes

Questions to answer What created our own great lakes? What created our own great lakes? Why does Illinois have such great soil? Why does Illinois have such great soil? What shape valley do glaciers make? What shape valley do glaciers make? glaciers U shaped

15.3 Ice ages Ice age- long periods of climatic cooling Ice age- long periods of climatic cooling Epochs/interglacial periods: times when it is warmer temperatures and no to low glacial movement. Epochs/interglacial periods: times when it is warmer temperatures and no to low glacial movement.

Canada’s ice age

Sea level actually drops during an ice age. It drops because the fresh water trapped in the ice keeps accumulating through the evaporation of the oceans. Sea level actually drops during an ice age. It drops because the fresh water trapped in the ice keeps accumulating through the evaporation of the oceans. The oceans are actually “saltier” during glaciations than during warm times. The oceans are actually “saltier” during glaciations than during warm times.

The Theories of Glaciations Causes: Causes: Milankovitch Theory- small irregular changes in the orbit and tilt of earth axis cause ice ages Milankovitch Theory- small irregular changes in the orbit and tilt of earth axis cause ice ages Previous theories: Previous theories: –Sun producing less heat –Volcanoes blocked sun’s rays –Continents blocked warm ocean currents

Questions to answer Are we in an ice age now? Are we in an ice age now? How long ago was the last ice age? How long ago was the last ice age? The oceans are actually _______ and _____ during glaciations than during warm times. The oceans are actually _______ and _____ during glaciations than during warm times. What is the current theory about glaciers What is the current theory about glaciers No we are in an epoch or interglacial period 14,000 years ago Saltier LOW Milankovitch Theory- small irregular changes in the orbit and tilt of earth axis cause ice ages