Week 8 Flash - Env 10

How do plate tectonics relate to environmental science? (impacts)

Plate tectonics impact ocean circulation, air circulation, evolution, resources, and give us data.

What is the elastic rebound theory?

When the build up of stress in rocks exceeds the strength of the rock, an earthquake will occur to release the stress.

Where do earthquakes occur?

At transform boundaies, spreading ridges, and subduction zones.

What is the benioff zone?

The seizmic zone which coinsides with the dip of a subducted plate.

At what depth do earthquakes stop?

The end of the benioff zone, 700 km.

Types of earthquake waves?

Pressure, shear, and surface waves.

P waves?

Compressional, fastest, travels through solids and liquids.

S waves?

Rippling, slower than p waves, travels through solids only.

Surface waves?

Slowest, causes most damage.

What is the focus point of an earhtquake?

Where the initial rupture occurs.

What is the epicenter of an earthquake?

Point on surface above the focus point.

How do we know the outer core is liquid using quake waves?

No s waves in the outer core because they cannot pass through liquid.

How do earthquakes causes damage?

90% of damage is caused by shaking, the rest is caused by landsides, liquefacation, differential settlement, fire, flood, and tsunamis.

What factors effect earthquake damage?

Earthquake magnitude, distance from epicenter, soil type, frequency, and focusing of waves.

How does California’s sediment effect earthquake damage?

It amplifies the motion caused by shaking, since there is a lot of water under.

What is magma?

Molton rock below Earth’s surface. It contains melt, crystals, and gases. SiO4 is main component.

What does water do to magma?

Water breaks the bonds of the SiO4 tetrahedra.

What are the magma types?

Mafic, intermediate, and felsic

Properties of mafic magma?

Low in SiO4 (silica), high in Fe and Mg (magnesium). Low in viscosity. Forms rocks like basalt (gabbro when underground). The magma is mafic.

Properties of felsic magma?

High in SiO2, low in Fe and Mg. High in viscosity. Forms rocks like Rhyolite/Granite.

Properties of intermediate magma?

Slightly higher in SiO2 than mafic magma, slightly lower in Fe and Mg. Medium viscosity. Forms andesite and dacite.

How does the amount of silica in a magma effect it?

More silica = more networks = trapped gas = more explosive.

Effusive volcano types?

Mid-ocean ridges, flood basalts/continental fissure eruptions, and shield volcanoes.

What is a continental fissure eruption?

Giant crack spew out massive amounts of lava, this is called a flood basalt.

What is a shield volcano?

Broad, flat volcanoes formed by mantle rising through oceanic crust, i.e. Hawaii.

Explosive volcano types?

Cinder cones, composite/stratovolcanoes, calderas.

What is a cinder cone?

Moderately explosive volcanoes made of pyroclastics, usually explode only once.

What are stratovolcanoes?

Mixture of pyroclast and lava, associated with subduction zones.

What is a pyroclast?

A bit of material expelled during a volcanic eruption. Ash, cinders, bombs, blocks.

What are calderas?

Forms via mantle rising through continental crust, collapsed center.

What are pyroclastic flows?

Aftermath of a volcanic explosion where erupted material and ash clouds flows down with gravity across the surface of the volcano and surrounding area.

Types of volcanic hazards?

Lahars, pyroclastic flows, volcanic ash, and lava flows.

What are lahars?

Fast flowing mudflows.

What does volcanic ash do?

Ash is essentially ground up silica, it disrupts aviation and spreads quickly.

How do eruptions affect global climate?

They inject SO2 in the atmosphere which then converts to H2SO4 (sulfuric acid). These aerosols increase albedo and cool. They eventually get washed out.