Glaciers and Glaciation Chapter 12

Glaciers and Earth’s Systems A glacier is a large, long-lasting mass of ice, formed on land, that moves downhill under its own weight Glaciers are part of Earth’s hydrosphere About 75% of the world’s supply of fresh water is locked up in glacial ice

*Paleozoic glacial age shows evidence for continental drift. *Glaciers when present are more effective in transportation and deposition than running water *Yosemite, Great Lakes, Glacier National Park, Greenland, Antarctica Glaciation *Ice Age covered 1/3 of land surface only a couple million years ago. *Rock record shows other older glaciations.

Formation of Glaciers Glaciers develop as snow is compacted and recrystallized, first into firn and then glacial ice A glacier can only form where more snow accumulates during the winter than melts away during the spring and summer –Glaciation occurs in areas cold enough to allow accumulated snow to persist from year to year

Formation of Glaciers Two types of glaciated terrains on Earth: –Alpine glaciation occurs in mountainous regions in the form of valley glaciers –Continental glaciation covers large land masses in Earth’s polar regions in the form of ice sheets

Anatomy of a Glacier An advancing glacier gains more snow than it loses, has a positive budget –End or terminus of glacier advances downslope A receding glacier has a negative budget –Terminus of glacier shrinks back upslope Snow is added in the zone of accumulation of glaciers, whereas melting (and calving of icebergs) occurs in the zone of ablation The equilibrium line, which separates accumulation and ablation zones, will advance or retreat depending on the climate

Receding Glacier South Cascade Glacier, Washington

Movement of Glaciers Valley glaciers move downslope under the force of gravity Movement occurs by basal sliding and plastic flow –Crevasses are fractures formed n the upper rigid zone Due to friction, glacier flow is fastest at the top center of a glacier and slowest along its margins slow fast

Glacial Erosion Glaciers erode underlying rock by plucking of rock fragments and abrasion as they are dragged along –Basal abrasion polishes and striates the underlying rock surface and produces abundant fine rock powder known as rock flour

Erosional Landscapes Erosional landforms produced by valley glaciers include: –U-shaped valleys –Hanging valleys Smaller tributary glacial valleys left stranded above more quickly eroded central valleys

Erosional Landscapes U-shaped valleys Hanging valleys

Glacial Deposition General name for unsorted, unlayered glacial sediment is till Lateral moraines are elongate, low mounds of till along sides of valley glaciers Medial moraines are lateral moraines trapped between adjacent ice streams Terminal moraines are ridges of till piled up along the front end of a glacier

Glacial Deposition Medial moraines are lateral moraines trapped between adjacent ice streams

Glacial Deposition Large amounts of liquid water flow over, beneath and away from the ice at the end of a glacier Sediment deposited by this water is known as glacial outwash Sediment-laden streams emerging from ends of glaciers have braided channel drainage patterns Outwash landforms include drumlins, eskers, kettles and kames Drumlins give direction information

Antarctic Ice Sheet

Past Glaciation from Ice Cores

Direct Effects of Past Glaciation Large-scale glaciation of North America during the recent ice age produced the following effects: –Soil and sedimentary rocks were scraped off in northern and eastern Canada, and lake basins were gouged out of the bedrock

Indirect Effects of Past Glaciation Large pluvial lakes (formed in a period of abundant rainfall) existed in closed basins in Utah, Nevada and eastern California –Great Salt Lake is remnant of much larger pluvial Lake Bonneville –Huge floods emanated as ice-dammed lakes (e.g., Lake Missoula) drained catastrophically Sea level was lowered by water locked up into ice sheets, allowing stream channels and glaciers to erode valleys below present-day sea level –Fiords are coastal inlets formed by drowning of glacially carved valleys by rising sea level Giant gravel ripples formed during draining of Lake Missoula Norway

Meteorites found in Arctic Glaciers The easiest place to locate dark, rocky meteorites is in Antarctic Ice Sheet A small number of meteorites appear to have come from the Moon and Mars Several of these appear to have come from Mars martian meteorite lunar meteorite

The Global Energy Challenge Roel Snieder Photo: USFWS/Susanne Miller

Developing countries

… and our energy use

Our energy-dependence (1)

Energy use by type (International Energy Outlook 2006)

Peak oil N.B. based on USGS estimates, these are among the most optimistic (Energy Information administration)

Peak oil (again)

Declining production (1) resource depleted Time Production supply

Declining production (2) production gap! Time Production demand supply

Oil Peak, Oil Panic ? (Study by Amos Nur - Stanford) U.S., Canada, Japan, Germany, France, Italy, UK, are the biggest consumers of oil reserves worldwide.

Countries with highest per capita income seeking oil from countries holding the oil wells/reservoirs (Saudi Arabia, Iraq, Venezuala).

New find in GOM (Jack No. 2 test well) up to 3-15 billion barrels of oil US consumption 20 million barrels/day 5 months - 2 years reservoir is 8 km under sea level

Non-convenional reserves (excluding gas and coal) Produced (gone) Proved Reserves Undiscovered(?) EOR Extra Heavy Oil & Tar Sands Shale Oil Trillions of Barrels Recoverable Years Supply at 2005 Production Unconventional petroleum resources: (more difficult & dirty, and therefore expen$ive) Conventional (“easy”) (Courtesy of Joe Stefani)

Non-conventional oil from National Geographic, June 2004 Tar Sand Heavy Oil shale 2 tons of tar sands produce 1 barrel of bitumen (~asphalt)

Other Energy Resources The metal uranium is used to power nuclear power generators –Found with organic matter in sedimentary rocks –Accounts for 10% of U.S. energy production –Leaves radioactive waste as by-product Hydroelectric power provides about 4% of U.S. energy needs –Renewable and non-polluting Geothermal power provides about 0.2% of U.S. energy needs Other renewable, non-polluting energy sources are wave/current power, solar power, wind power, and hydrogen fuel cells –As fossil fuel supplies dwindle, these sources become more important

A New, Global Oil Quandary: Costly Fuel Means Costly Calories (NYT, January 19, 2008) Rising prices for cooking oil are forcing residents of Asia’s largest slum, in Mumbai, India, to ration every drop. Bakeries in the United States are fretting over higher shortening costs.

Carbohydrates and biofuel Do we feed humans or cars? Is it a good idea to compete with our machines for calories? glucose cellulose

Research: biofuel from cellulose Feed cost ($/GJ) Processing costs ($/GJ) oil (100$/barrel) gas starch (glucose) cellulose vegetable oil (Figure adapted from Lange, J.P., Biofuels, Bioproducts and Biorefining, 1: 39-48, 2007)

First solar 2 MW array Ft. Carson, CO

Research: efficient solar cells

Alternative Energy Sources: Wind power

Past Glaciation from Ice Cores

Arctic sea ice (National Snow and Ice Data Center, Boulder)

Arctic sea ice (National Snow and Ice Data Center, Boulder) 4.3 million sq km

What can I do as consumer? LightingTransportationAppliances

What can I do as citizen? Ask: what is our energy plan? Start a discussion in your community. Demand that the United States becomes a world- leader in responsible use of energy. “That which we are, we shall teach, not voluntarily but involuntarily.” [Emerson] z

Temperature and CO 2 records now Thousands of year before present Temperature change ( o C) Carbon Dioxode (ppmv)