Glaciers and Ice Ages

1. Glaciers andIce Ages By: Briana Brandt and Lindsey Kosinski

2. What is a glacier? • Glacier: a massive, long-lasting, moving mass of compacted snow and ice • Glaciers covered the land 10,000 to 20,000 years ago. • 2 types: • Alpine Glacier • Continental Glacier

3. How Glaciers Form… • Where do they form? • On land where the amount of snow that falls in the winter exceeds the amount that melts in summer; must have cool temperatures in summer • They form in 2 types of environments: • High, snowy mountains in any climate; Alps • Cold polar regions; Antarctica

4. Glaciers • How do glaciers form? • Glaciers begin to form when snow remains in the same area year-round • Each year, new layers of snow bury and compress the old layers • This compression forces the snow to re-crystallize, forming grains similar in size and shape to grains of sugar • After about two winters, the snow turns into firn -- an intermediate state between snow and glacier ice • Snow ->Granual ->Firn -> Glacier

5. GlacialMovement • Glaciers begin to move when there is an increase in pressure. • 2 Types of movement: • Basal slip: movement of the entire mass of a glacier along the bedrock • Plastic flow: ice flows as a thick fluid because of an increase in pressure

6. Glacial Movement • Glacial Erosion: • Glacial Striations: parallel grooves and scratches in bedrock that form as rocks are dragged along at the base of a glacier • These markings show the direction of ice movement and are used to map the flow directions of glaciers.

7. Glacial Movement • Landforms created from glacial erosion • From Alpine Glaciers • Forms U-Shaped Valleys, tarns, horns and hanging valleys • From Continental Glaciers • Forms vast regions- entire mountain ranges • Formed the Great Lakes and the Finger Lakes in New York

8. Ice AgeS • What are ice ages? • Ice Ages: intervals of time when large areas of the surface of the globe are covered with ice sheets • The most recent ice age is the Pleistocene Ice Age • This occurred 2 million years ago in the Northern Hemisphere.

9. Ice Ages • When did ice ages occur? • Glaciations are concentrated into 4 time intervals. • Proterozoic Age (between 800 and 600 million years ago) • Pennsylvanian and Permian Age (between 350 and 250 million years ago) • Late Neogene to Quaternary Age (the last 4 million years) • Ordovician and Silurian Age (between 460 and 430 million years ago) • Less extensive glaciations.

10. Ice Ages • Why do Ice Ages occur? • Because of the change of continental positions. • Because of the uplift of continental blocks. • Because of the reduction of CO2 in the atmosphere. • Because of changes in the Earth’s orbit.

11. Ice Ages • What controls the advance and retreat of glaciers? • Changes in the eccentricity of the Earth’s orbit • Changes in the tilt of the Earth’s axis • The precession of the equinoxes

12. Works’ Cited http://nsidc.org/glaciers/index.html http://www.google.com

13. Study Questions… • What are the two types of Glaciers? • Alpine and Continental • What are the two types of environments that Glaciers form? • High, snowy mountains and cold polar regions • What are the four stages of glacier formation? • Snow, Granual, Firn, Glacier • What is the most recent ice age? • Pleistocene • Glaciations are divided into how many time intervals? • four