Introduction to Glaciation

New York and the Ice Ages

Glaciation

• Various types of paleo-climatic evidence suggest that the climate of the Earth has varied over time. The data suggests that during most of the Earth's history, global temperatures were probably 8 to 15° Celsius warmer than they are today. However, there were periods of times when the Earth's average global temperature became cold.

Glaciers• Glaciers are accumulations of ice large

enough to survive the summer melt.• In present day New York State, the climate

is too warm to support glaciers even at the highest elevations.

• However, 20,000 years ago, a great continental ice sheet covered most of New York State and the northern most areas of the country.

How do glaciers advance?

• When Ice forms under the weight of accumulating layers of snow, it will begin to flow downhill, or away from its thickest accumulation.

Cómo se forman y se mueven los glaciares

• Los glaciares se forman en las regiones donde se acumula la nieve y permanece sobre el suelo todo el año.

• Cuando la nieve no se derrite, se acumula lentamente y su peso aumenta tanto, que las capas mas profundas se comprimen y se convierten en hielo.

Cómo se forman y se mueven los glaciares

• Finalmente, puede haber suficiente presión sobre el hielo para que éste obtenga una consistencia plástica.

• La masa comienza lentamente a fluir sobre la capa inferior plástica y el glaciar se mueve cuesta abajo.

What are Valley Glaciers?

• Also known as Alpine glaciers occur in mountain regions and often carve out U-shaped valleys during their steady advance.

• Alpine glaciers are also known as valley glaciers.

Los Glaciares de Valle

• Ocurren incluso con las actuales temperaturas globales mas cálidas. En las montanas altas, donde la temperatura no derrite la nieve durante el verano, los glaciares de valle siguen creciendo y arrastrándose.

Peru: Andes

Argentina: Perito Moreno Glacier

Alpine Glaciers

What are Continental Glaciers?• Continental glaciers, also known as ice

sheets, are the type of glacier responsible for most of the glacial features found throughout New York State.

• The erosion caused by a glacier is not the result of ice rubbing against rock. Rather, it is the rock carried within the glacier or dragged under its flowing ice that causes most glacial erosion.

Los glaciares continentales

• Hoy en día, los glaciares continentales solo cubren un 10% de la tierra, sobre todo cerca do los polos, en la Antártica y Groenlandia.

• Estos glaciares continentales son enormes masa de hielo y nieve.

• En el pasado, los glaciares continentales cubrían un 28% de la tierra.

Advancing Ice Sheets

• As the ice sheet advances over a region, the rock-encrusted ice acts like sandpaper.

• It smoothes the jagged edges from the mountains and polishes the hard bedrock surfaces.

• Rocks within the glacier also leave parallel grooves and scratches in the bedrock forming striations.

Glacial Striations - Utah

What shape does a valley eroded by a glacier is usually have?

• U-shaped

U-shaped Valley

Glacial Landforms

Glacial Features of Deposition

• In addition to creating features through erosion, the ice sheets also create features through deposition of unsorted glacial sediment (till).

• Accumulations of rock and soil that build up in front of the flowing ice forms deposits called drumlins as the ice moves up over these hills of sediment.

• Drumlins are elongated tear-drop shaped hills.

Nova ScotiaKejimkujik National Park

Drumlins

• Glacial erratics were rafted in on icebergs during the Missoula Floods.  This granite boulder was probably transported about 200 miles from what is now the Idaho/Montana border!