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 Glaciationfrom 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 ChallengeRoel Snieder

Photo: USFWS/Susanne Miller

Developing countries

… and our energy use

Our energy-dependence (1)

Energy use by type

(International Energy Outlook 2006)

Peak oilPeak oil

N.B. based on USGS estimates, these are among the most optimistic

(Energy Information administration)

Peak oil (again)

http://info.energyscenariosireland.com/Overview

Declining production (1)

resource depleted

Time

Pro

duct

ion

supply

Declining production (2)

production gap!

Time

Pro

duct

ion demand

supply

Oil Peak, Oil Panic ?(Study by Amos Nur - Stanford)

U.S., Canada, Japan, Germany, France, Italy, UK, are the biggestconsumers 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(?)

EORExtra Heavy Oil& Tar Sands Shale Oil

0 1 2 3 4 5 6 7 8 9 10

Trillions of Barrels Recoverable

Years Supply at2005 Production

Unconventional petroleum resources:(more difficult & dirty, and therefore expen$ive)

Conventional(“easy”)

0 25 50

(Courtesy of Joe Stefani)

Non-conventional oil

from National Geographic, June 2004

Tar Sand

HeavyOil

Oilshale

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

0 5 10 15 20 25 Feed cost ($/GJ)

25

20

15

10

5

Pro

cess

ing

cost

s ($

/GJ)

oil (100$/barrel)

gas

starch(glucose)

cellulose

vegetableoil

http://gcep.stanford.edu/research/biomass.html(Figure adapted from Lange, J.P., Biofuels, Bioproducts and Biorefining, 1: 39-48, 2007)

First solar 2 MW arrayFt. Carson, CO

Research: efficient solar cells

ﾠ

1 mm

http://gcep.stanford.edu/research/solar.html

Alternative Energy Sources: Wind power

Past Glaciationfrom Ice Cores

Arctic sea ice 1995-2007

(National Snow and Ice Data Center, Boulder)

Arctic sea ice 2005-2007

(National Snow and Ice Data Center, Boulder)

4.3 million sq km4.3 million sq km

What can I do as consumer?

Lighting Transportation Appliances

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 CO2 records

1 350 300 250 200 150 100 50 now

Thousands of year before present

20

-2-4-6-8

-10

Tem

pera

ture

cha

nge

(o C)

400

350

300

250

200

Car

bon

Dio

xode

(pp

mv)