Chapter 9 Notes: Ice and Glaciers, Wind and Deserts

Size: px

Start display at page:

Download "Chapter 9 Notes: Ice and Glaciers, Wind and Deserts"

Peter Cross
5 years ago
Views:

1 Chapter 9 Notes: Ice and Glaciers, Wind and Deserts *Glaciers and Glacial Features glacier is a mass of ice that moves over land under its own weight through the action of gravity Glacier Formation must be sufficient enough moisture in the air to provide the necessary precipitation winter snowfall must exceed summer melting in mountains, start as snow patches that survive summer slopes that face poles are protected from strongest sun weight of overlying snow pack It down and drives out air, causes it to recrystallize into a coarser, denser form (firn), intermediate texture between snow and ice and compact to solid interlocking crystals mass of ice become so large it flow downhill moving ice is a true glacier Types of Glaciers 2 types based on size and occurrence 1) Alpine glaciers Mountain or valley glaciers 70, ,000 2) continental glaciers ice caps: less than 50,000 square km ice sheets are larger can cover whole continets and reach 1km thickness Greenland and Antartica Movement and Change of Glaciers Flow is plastic, different parts of glacier move at different rates Base of glacier moves slower than higher more central parts Glaciers sometimes surge at rates of several tens of meters per day Glacier may slide on meltwater accumulates at base of ice. Surges occur when meltwater is dammed up and prevented from draining away until an unusual large quatity has built up and lubricate slide downhill Advancing edge of glacier eventually terminates. May flow out over water, break and create icebergs, known as calving

2 ablatiinl set of processes by which ice is lost from a glacier equilibrium line: line on the glacial surface where there is no net gain or loss of material advancing and retreating in glaciers Glacial Erosion and Deposition alpine glaciers carve U shaped valley typically striations: very small scale, bits of rock become frozen into ice at base make parallel scratches abrasion: erosion by scraping of ice or included sediments on surface underneath ice moves on, small bits of rock are torn away in plucking plucking at head contributes to formation of a cirque, bowl shaped depression alpine glaciers flow side by side, wall of rock between them to may be a sharp ridge, arête erosion by several glaciers around a single peak produces a horn till: sediment deposited directly by ice angular and poorly sorted material outwash: till transported and redeposited by the meltwater continental drift moraine: landform made of till end moraine terminal moraine Ice Ages and Their Possible Causes interglacials ice sheets retreated *Wind and its Geologic Impacts Wind Erosion consists of: 1)wind abrasion: wearing away of a solid object by the impact of particles carried by wind where wind blows consistently from certain directions, exposed boulders may be planned off in the directions from which they have been abraded becoming ventifacts 2)deflation: wholesale removal of loose sediment, usually fine grained sediment, by the wind

3 desert pavement Wind Deposition Dune: where sediment transported and deposited by wind, the principle depositional feature is a low mound or ridge usually made by sand Dune Migration pile up at the peak, tumble down steeper face, slip face, which tends to assume a slope at angle of repose of sand layer upon layer of sediment slides down the slipface, slanted crossbeds develop in the dune Loess deposit of windblown silt *Desert and Desertification deserts: region with so little vegetation that only a limited population can be supported on the land desertification: generally restricted to apply only to the relatively rapid development or expansion of deserts caused or accelerated by the impact of human activities arid: annual rainfall less than 250 mm semiarid: mm

4 10/09/2013

5 10/09/2013

MASS MOVEMENTS, WIND, AND GLACIERS

Date Period Name MASS MOVEMENTS, WIND, AND GLACIERS SECTION.1 Mass Movements In your textbook, read about mass movements. Use each of the terms below just once to complete the passage. avalanche creep