Glaciers and Earthquakes

Glaciers

• Largest reservoir of fresh water

• Move under their own weight

• Very sensitive to climate change

Types of Glaciers

-Continental and Alpine

Continental Glaciers

• Only found in the poles

• “Self-flattening” – gravity causes ice to move away from middle towards thinner edges

Alpine Glaciers

• Aka Valley Glaciers

• Originate high up in the mountains

• Flow controlled by the slope of the surface

Continental Glacial Erosion

-Flat bedrock surfaces

-huge, slow-moving ice sheets scrape and carve the land as they move.

Alpine Glacial Erosion

• U-shaped valleys

• Glacial Lakes

-smaller glaciers in the mountains carve and shape the land as they move downhill.

Glacial Deposits (Supraglacial):

-top of ice

• Moraines – end of glacial deposits/movement

• Englacial sediment – sediment gets incorporated into the body of the glacier

Glacial Deposits (Subglacial):

-below ice

-Glacial till: mixture of fine and course sediment

Earthquakes

-linked to plate boundaries 

Mid-Ocean Ridge Earthquakes

-where two ocean plates are pulling apart.

-the plates are pulling apart, the crust breaks, and that shaking is an earthquake.

Subduction Zone Earthquakes

-happen where one tectonic plate is being pushed under another.

-These are some of the strongest earthquakes on Earth because the plates are stuck together so tightly before they snap.

-The heavier plate gets forced down into the Earth (this is “subduction”).

• As the plates press, bend, and scrape against each other, they build up a lot of pressure.

• When that pressure suddenly releases, it causes a big earthquake

Intraplate Earthquakes

-happen in the middle of a tectonic plate, not at the edges.

-Most earthquakes happen where plates meet—but intraplate ones happen far away from plate boundaries.

• Stress builds up inside the plate from old faults or pressure moving through the plate.

• When that stress releases, the ground shakes

Faults form when?

Tectonic forces add stress to rock

Types of stress

-compression, tension, and shear.

Elastic Rebound

-explains how earthquakes happen.

-the crust bends, snaps, and releases energy.

Focus 

• the exact spot underground where the earthquake starts.

• It’s where the rocks first break and energy is released.

Epicenter

• the spot directly above the focus on Earth’s surface.

• It’s the place on the ground that usually feels the shaking the strongest.

Focus and Epicenter difference 

• Focus = the underground starting point of the earthquake.

• Epicenter = the surface point right above the focus.

-So, the focus is below ground, and the epicenter is on top of the ground in that same line.

Divergent Plate Boundaries

-two tectonic plates are moving away from each other.

Convergent Plate boundaries

-two tectonic plates push toward each other.

Faults

-planar breaks in the crust. Most faults are sloping (vertical faults are rare). The type of fault depends on the relative motion of blocks. Stress type?

Earthquake Sequence

• Foreshocks – smaller earthquakes occurring before the mainshock

• Mainshock – Largest earthquake in the series

• Aftershocks – smaller earthquakes occurring after the mainshock