MR.GREEN - Glacial & Global Climate Change VOCABULARY
Terms in this set (16)
What is SNOWBALL EARTH?
The period between 500 MYA - 1 BYA, when the earth was iced over, maybe several times; glaciers covered the whole planet, they may have even reached as far as the equator.
Why did SNOWBALL EARTH happen?
Back then, the earth had a younger, fainter sun, and the weathering of silicate rocks had reduced the CO2 levels, which reduced the greenhouse effect. The continents had been clustered near the equator, reflecting a lot of solar energy.
How do we know SNOWBALL EARTH happened?
Not only were drop-stones found near the equator, but banded iron formations indicated massive die offs of cyanobacteria.
What was the cycle to SNOWBALL EARTH?
continents reflect heat -> earth get colder -> glaciers advance from poles -> glaciers reflect heat -> cycle repeats.
Why and how did SNOWBALL EARTH end?
Volcanic out-gassing plus no photosynthesis beget wicked high levels of CO2, about 350 times higher than today, which brought on a super green house effect.
How do we know the CRETACEOUS PERIOD happened?
We have climate information from fossilized plankton, foraminifera. The fossils were analyzed for levels of carbon and oxygen isotopes, which provided temperature and gas levels from ancient climates.
What was the climate like during the CRETACEOUS PERIOD?
The high surface sea temperature was about 31F degrees higher than today; CO2 levels were two to six times higher than now. There was no polar ice, thus high sea levels.
How long has the earth had modern ice ages?
Over the past few million years, the earth has had long ice ages separated by short inter-glacial periods.
What are ice ages caused by?
Ice ages are caused by the MILANKOVITCH CYCLES which are variations in the earth's orbit.
How do we know modern ice ages happened?
We got this data from ice cores.
How do glaciers form?
Glaciers are created by a sequence of cool summers brought by the MILANKOVITCH CYCLES or when more snow falls in the winter than it melts in the summer. So, snow accumulates and is compacted under the weight of more snow.
What are the steps for snow to form into glacial ice?
snow -> granular ice -> firn -> glacial ice
What is a CONTINENTAL GLACIER?
EX//: Antarctica and Greenland.
Found in polar regions, a CONTINENTAL GLACIER is an ice sheet that covers an entire land mass. They get squashed in all directions.
What is an ALPINE GLACIER?
Mountain glaciers that descend down mountain valleys: looks like a river of ice.
When does PLASTIC FLOW occur?
When ice is under enough pressure that it can achieve PLASTICITY, meaning that it can be molded without breaking. Often referred to as flowing like cold molasses.
What is BASAL SLIP?
When ALPINE GLACIERS slide downward on a thin layer of water.
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