Lecture 2 Geology and Climate Flashcards
Ice Ages (4)
- Long-term drop in global temperatures
- Extension of continental ice sheets
- Cyclical, generally every 44k-110k years
- Earth has experienced at least 5 major Ice ages
What was the Pleistocene Epoch?
The most recent Ice age that lasted from ~2million years ago to ~8thousand years ago
Pleistocene Epoch Ice sheets (4)
- Pleistocene Epoch lead to Regular growth and decay of Northern ice sheets
- Up to 20 glacial advances and retreats during its time
- Massive ice sheets up to 3-4 km thick
- covered 1/3 earth’s land masses
Ice Sheets (3)
- Ice sheets form in areas where winter snow does not melt entirely over the summer.
Over thousands of years, piles up into thick masses of ice - Grow thicker and denser as the weight of new snow and ice layers compresses the older layers.
- Becomes stronger as it becomes heavier
How Ice sheets affected northern geology (2)
As the Ice sheets expanded and contracted they caused 2 things to happen:
1. Eroding of the Canadian shield
2. Deposition of sand and slit
The Canadian Shield (3)
- Remnants of earth’s original crust formed ~2.5 billion years ago
- no longer visible in areas – overlaid by sedimentary rock (limestone)
- very evident along coastline in Churchill – evidence of scraping & scouring during ice ages
Lake Agassiz (7)
-75,000 years ago interglacial warming was taking place
- Laurentide Ice sheets blocked meltwater from moving out into the Hudson Bay area
- Formed a huge freshwater lake called Lake Agassiz
- Covered most of mid-continent, including Manitoba, over its 5000 year history
- Emptied 8000 years ago when the last ice sheet in Hudson Bay disintegrated
- Left areas in north depressed by water and ice
-When ice dam broke, the depression filled with marine water, and became Tyrrell Sea
Isostatic rebound (3)
- The weight of Large ice-sheets can cause the Earth’s surface to sink
- When ice sheets melt, the load on the crust and mantle is decreased = rebound back to an equilibrium level
- Beach ridges: new shorelines were repeatedly formed as the old shorelines are elevated
Glacial landforms created by the retreat of glaciers (4)
Moraine – accumulation of glacial debris at the edge of a glacier
Eskers - Sedimentary material (gravel or sand) deposited by streams flowing under or through glacial ice
Kame – a hill or hummock composed of stratified sand & gravel laid down by glacial meltwater. Accumulates in a depression on a retreating glacier, then is deposited on the land surface with further melting
Kettle hole – a hollow created when buried blocks of glacier ice melt out of the earth
Major environmental changes caused by glacial cycles (3 + how it effects)
- climate patterns and zones
- location and extent of habitat
- routes of dispersal
effects the distribution of species in space and through
time (biogeography)
What can individual species do when their environment changes (3)
- Move
- Adapt
- Go extinct
Environmental changes for individual species - moving (3)
- Shift in their distribution follows physical changes in their environment
– Many species moved south of ice sheets
– Can’t always move though!
Environmental changes for individual species - Adapting (2)
- Adapt to new conditions in original habitat
- Does the genetic diversity exist to cause this adaptation?
Environmental changes for individual species - possible Extinction (3)
- Undergo severe range contractions (use refugia) and possible extinction
– Can lead to isolation, genetic drift
– Loss of genetic diversity for future adaptation
Refugia definition
Refugia = Areas that provide suitable habitat for
relict species; have not undergone ecological changes
