Flashcards in Ice Levels Over Time Deck (25)
What type of periods does the earth have?
The earth goes through cold periods, how long do these last?
Millions of years.
Called ice ages.
What happens during ice ages?
Large masses of ice cover parts of the Earth's surface.
What and when was the last ice age?
Began around 2.6 million years ago.
During ice ages what are the cooler periods called?
What happens during glacial periods?
Ice advances to cover more of the Earth's surface.
Each one lasts about 100,000 years.
In between glacial periods there are what?
Warmer periods called interglacial periods.
What happens during interglacial periods?
Ice retreats to cover less of the Earth's surface.
Each one lasts about 10,000 years.
When did the last glacial period begin and end?
Began - 100,000 years ago.
Ended - 10,000 years ago.
When did ice cover much more of the earths surface?
20,000 years ago.
Since the beginning of the pleistocene what has there been?
Permanent ice sheets on Greenland and Antarctica.
What % of land was covered in ice during the last glacial period?
What are we currently in?
An interglacial period that begun 10,000 years ago.
Today how much of the earths surface is covered in ice?
What are ice sheets?
Huge masses of ice that cover whole continents.
What are glaciers?
Masses of ice which fill valleys and hollows.
Evidence of changing temperature comes from where?
Three main sources.
What are the 3 main sources changing temperatures comes from?
Chemically what changes as temperature changes?
Chemical composition of ice.
Why does chemical composition of ice and marine sediments change as temperature changes?
So they can be used to work out how global temperature has changed in the past.
Ice and sediments build up over thousands of years, so what is taken?
Samples taken at different depths show the temperature over thousands of years.
Some landforms we see today were created by what?
Glaciers in the past.
Some areas that aren't covered in ice today were covered in ice in the past, what does this mean?
Temperatures were lower.
The remains of some organisms are persevered when they die, what does this create?