Chapter 18- Glaciers and Ice Ages

Glacial ice has less than ____% air.

20%

How far back does the temperature record go using Antarctica Ice cores?

450,000 years ago

How many major ice ages has the Earth experienced?

5

What is the amount of air in loose snow?

90%

What is an end moraine?

A pile of till left at the toe of the glacier left behind after a glacier melts

What is a hanging valley?

A valley above the main trunk of the glacier, created by tributary glaciers

When was the last glacial maximum?

About 22 thousand years ago at the end of the Pleistocene

What is a medial moraine?

Accumulation of till created when two alpine glaciers converge

What is a lateral moraine?

Accumulation of till of the side of the glacier as it carves through the valley

If accumulation exceed the loss of ice, the glacial front _____.

Advances

What are the 2 main types of glacier?

Alpine (also known as mountain glacier) and continental (also called ice sheets) glacier

What is a terminal moraine?

An end moraine that was deposited at the farthest limit of glaciation

What are the 3 cycles that affect the amount of summer sunlight?

Axis tilt, eccentricity, precession

What is a cirque?

Bowl-shaped depression located at the head of the glacier

What is a glacier?

Compressed ice that accumulated on land over many years of snowfall and that moves under its own weight. Note: A glacier has tobe moving to be considered a glacier.

Is Antarctica an example of a mountain or continental glacier?

Continental

In the upper zone of a glacier, abovethe brittle-plastic transition, where the ice is brittle, _____ form.

Crevasses

What is a fjord?

Deep steep-sided inlet that are drowned glacial troughs that form when sea level rises

When a glacier advances over a ground moraine, what kind of feature is often created?

Drumlin

A large bolder deposited by a glacier is called an ____.

Erratic

When meltwater forms in a channel under a glacier, a sinuous ridge is formed of stratified sediment. After the glacier retreats, the ridge is called an ___.

Esker

Does the center and top of the glacier move faster or slower that the bottom? Why?

Faster, there is no drag or friction from the substrate

When snow becomes compacted and is only about 25% air, this is called ____

Firn

What is the general term for all sediment of glacial origin?

Glacial Drift

A valley that is U-shaped indicates that it was formed by _____.

Glaciers

An alpine glacier move downhill because of _____. A continental ice sheets spreads outward from their center because of ____.

Gravity; gravity

Describe the positive feedback loop related to ice?

Ice causes reflection of solar radiation so more ice results in cooler temperatures which causes more ice.

What is the equilibrium line?

Marks the boundary between the zone of accumulation and the zone of ablation

When the Earth is more tilted, is there more or less summer sunlight?

More

Has it always been the case that when the Earth is closest to the sun that the season is winter? Why?

No, because 13,000 years ago the Earth's axis was tilted in the opposite direction

What isotope, found in ice cores, do we often use to determine past temperatures on Earth?

Oxygen-18

The ground of some permafrost areas splits into pentagonal or hexagonal shape, resulting in a landscape called ______.

Patterned Ground

A term for permanently frozen ground is _____.

Permafrost

A valley glacier that extends outward onto a flat plain of land is called a _____ glacier.

Piedmont glacier

In the zone below the brittle-plastic transition, _____ deformation occurs in the ice.

Plastic

Glaciers move either through ____ flow or by _____ on a layer of meltwater at their base.

Plastic; slipping or sliding (this is called basal slip)

Are the deposits strewn across the ground by glaciers well-sorted or poorly-sorted?

Poorly-sorted

What is causing parts of Canada and northern Europe to get higher?

Post-glacial rebound (or glacial isostatic adjustment) due to adjustment of the viscous mantle because of the retreat of glaciers

What is one of the problems associated with a warming climate related to permafrost?

Release of greenhouse gases, especially methane, which add to warming

If the loss of ice (ablation) exceeds accumulation, the glacial front ____.

Retreats

What happens to sea level during a glacial period?

Sea level falls because water is tied up in glaciers

What is an arete?

Sharp ridge of rock that separates two adjacent cirques

If the glacier is retreating, the glacier is getting larger or smaller?

Smaller

What does the term "sorting" mean?

The degree to which sediment has been separated by flowing currents into different-sized fractions.

What does the orientation of glacial striations tell us?

The direction of movement of a glacier

What does the shape of the drumlin tell us?

The direction that the glacier was moving, with the glacier flowing toward the less steep side.

What are Milankovitch Cycles?

The pattern in the Earth's orbit and rotation and Earth's position relative to the Sun and other planets that explains why ice ages happen when they do

If the glacier is retreating, what is the position of the toe of the glacier?

The toe moves back toward the origin of the glacier

Unsorted and unlayered sediment deposited when a glacier melts is called _____.

Till

Is the sediment within a drumlin sorted or unsorted?

Unsorted, since it is till

How do you know that an erratic is deposited by a glacier?

Water and wind could not move such a large bolder.

Why are the temperatures so different on the Earth and Moon?

We have an atmosphere

What is the difference between weather and climate?

Weather is temporary. Climate describes the typical weather conditions in an entire region for 30 years or more.

What is a horn?

Where 3 aretes or cirques meet forming a sharp peak

Why is it warmer when the Earth is farthest from the sun?

because the tilt of the axis plays a larger role, but the distance does moderate the season

What are the possible causes of a major ice age?

changes in Earth's atmosphere caused by the activity of organisms, volcanism, or dust/debris in atmosphere; plate tectonics where continents block the movement of ocean currents which affect climate

Chunks that calve off the glacier when it meets the water, are called an _____.

iceberg

Periods between ice ages or glacial cycles are called ___.

interglacials

Name some of the gases that can absorb infrared heat and radiate it back down to Earth, sometimes called greenhouse gases?

nitrous oxide, carbon dioxide, methane, and water vapor

What is stratified drift?

sediments sorted by size and weight laid down by glacial meltwater (Remember that the sediments are deposited by flowing water, and as water loses energy on a flat surface, the heavier sediments are deposited first, then the lighter sediments are deposited. This is how they become stratified.)

What is the "zone of ablation"?

the area where there is a net loss of glacial ice due to melting and calving

What is the glacial budget?

the balance between accumulation and loss of ice

If accumulation exceeds the loss of ice, what happens to the snowline (or equilibrium line)?

the equilibrium line moves down toward the area of wastage (or ablation)

What is a ground moraine?

till left at the base of the glacier as the glacier melts away

The fact that an esker is composed of stratified sediment indicates it was deposited by _____.

water

What is the "zone of accumulation"?

where the snow falls