Glaciers and Ice Ages By: Briana Brandt and Lindsey Kosinski

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

How Glaciers Form… Where do they 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 High, snowy mountains in any climate; Alps Cold polar regions; Antarctica Cold polar regions; Antarctica

Glaciers How do glaciers form? How do glaciers form? – Glaciers being 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

Glacial Movement Glaciers begin to move when there is an increase in pressure. Glaciers begin to move when there is an increase in pressure. 2 Types: 2 Types: – 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

Glacial Movement Glacial Erosion: 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. These markings show the direction of ice movement and are used to map the flow directions of glaciers.

Glacial Movement Landforms created from glacial erosion Landforms created from glacial erosion – From Alpine Glaciers Forms U-Shaped Valleys, tarns, paternoster lakes, horns, arêtes, hanging valleys, fjords (p. 314) Forms U-Shaped Valleys, tarns, paternoster lakes, horns, arêtes, hanging valleys, fjords (p. 314) – From Continental Glaciers Forms vast regions- entire mountain ranges Forms vast regions- entire mountain ranges Formed the Great Lakes and the Finger Lakes in New York Formed the Great Lakes and the Finger Lakes in New York

Ice AgeS Ice AgeS What are 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 The most recent ice age is the Pleistocene Ice Age – This occurred 2 million years ago in the Northern Hemisphere.

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

Ice Ages Why do Ice Ages occur? Why do Ice Ages occur? – Because of the change of continental positions. – Because of the uplift of continental blocks. – Because of the reduction of CO 2 in the atmosphere. – Because of changes in the Earth’s orbit.

Ice Ages What controls the advance and retreat of glaciers? 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

Works’ Cited Works’ Cited

Study Questions… 1. What are the two types of Glaciers? Alpine and ContinentalAlpine and Continental 2. What are the two types of environments that Glaciers form? High, snowy mountains and cold polar regionsHigh, snowy mountains and cold polar regions 3. What are the four stages of glacier formation? Snow, Granual, Firn, GlacierSnow, Granual, Firn, Glacier 4. What is the most recent ice age? PleistocenePleistocene 5. Glaciations are divided into how many time intervals? fourfour