Part 3: Glaciers & Ice Flashcards
- Define Glacier
A glacier is a large mass of ice on land that shows evidence of moving or having once moved
- How much of Earth is covered in ice today?
Approximately 10% of the Earth’s surface is covered with glacial ice
- Difference between wet and dry glaciers and how they move.
A “wet glacier” is one that slides on a thin layer of meltwater beneath the ice
The base of the glacier is frozen to the ground so it doesn’t move: the ice itself must move through plastic deformation. This type of glacier is referred to as a “dry glacier.”
- Define what happens Sublimation
sublimation (the transformation of solid “water” directly to a vapor or gas)
- Sequence from snow to glacier ice, what’s it called? What are the 4 steps?
1) The first stage is SNOW, about 90% air and fluffy
2) Stage two is when the snow compacts and forms small, equant, dense grains called GRANULAR SNOW. It is about 50% air
3) As the granular snow compacts even further, it becomes even denser with only 20-30% air and is called FIRN
4) The resulting GLACIAL ICE is less than 20% air, which is found in small bubbles in the ice
- Define Erratic
these rocks are out of place with respect to the surrounding material, they are called erratics or “exotics” because they “don’t belong.”
- Moraines
- left behind as the glacier retreats
- found in many different locations with respect to the glacier and each has a differentiating name
- moraines do not give as much information about the overall direction of glacial movement, but it does indicate the path the individual glaciers take through the valleys.
45A. Different Types of Moraines (End/Terminal)
End moraines pushed together at the ice front,
with the terminal moraine marking the maximum advance of the glacier
45B. Different Types of Moraines (Lateral/Ground)
Lateral moraines are the eroded dirt and rock incorporated into the ice at the sides of the valley
and the ground moraines are layers of drift beneath the ice.
45C. Different Types of Moraines (Medial)
are deposited where lateral ice streams join the main ice stream
- When did ice age officially end?
By 10,000 years ago, all the glaciers around the world were in retreat so we have chosen that time to delineate the end of the last Ice Age and the beginning of our most recent Interglacial period
- Define Striation
Loess indicates a glacier was present but tells nothing about direction.
These grooves or gouges are called striations and show the direction of movement of the ice
- Define Drumlins*
Drumlins are large streamlined hills of till and bedrock that form parallel to the direction of movement
- Define Fjord? How is it formed?
When sea level rises, it fills those U-shaped valleys with water. This is a fjord
- Define Glacier Drift
Glacial drift or till is the unstratified, poorly sorted sediment of heterogeneous sizes that collects around glaciers
