Flashcards in EQ1 Deck (56)
dense-10 to 12 g/cm³
iron and nickel
less to medium density-3 to 5 g/cm³
phases of liquid and solid-partially molten
what is the mantle made of?
peridotite=igneous rock made of minerals olivine and pyroxine
lower-more magnesium silicate
what waves pass through the crust?
surface and body waves can pass through.
what waves pass through the mantle?
body waves pass though at variable rates due to changes in density.
what waves pass through the outer core?
outer core=liquid (generates magnetic field)
only p waves can pass through, so an s wave 'shadow zone' is created.
what waves pass through the inner core?
only p waves reach the inner core and pass through but their refraction at the core mantle boundary creates a ring p wave 'shadow zone' between 105 and 140 degrees from the focal point.
what is the hypocentre?
'focus' point within the ground where seismic waves are first released.
what is the epicentre?
point on land directly above the hypocentre.
where are the active intra plate volcanoes?
1) east africa
what is happening in the east african rift zone?
actively splitting African and Arabian plate meet at a triple junction, where the Red Sea meets the Gulf of Aden. When the crust stretches beyond its limits, tension cracks begin to appear on earth's surface. Magma rises and squeezes through these widening cracks, sometimes erupting and forming volcanoes.
what is the Benioff zone ?
an area of seismicity corresponding with the slab being thrust downwards in a subduction zone
what is an example of a constructive plate boundary ?
mid Atlantic ridge
what is an example of a destructive plate boundary ?
Nazca plate and South American plate - andes mountains
what is an example of a conservative plate boundary ?
Pacific plate (faster) and North American plate (slower)
San Andreas fault
What's an example of a collision boundary ?
Indian plate and Eurasian plate
What activity happens on constructive plate boundaries?
submarine volcanoes which may become islands
What activity happens on destructive plate boundaries ?
Earthquakes- depth up to 700km
What activity happens at conservative plate margins ?
Shallow/ medium focus earthquakes
Ridges and scars on surface
What activity happens on collision plate margins ?
Shallow focus earthquakes
What happens at constructive plate margins ?
Decompression in the asthenosphere due to gap between the plates enables magma to rise, it cools and spreads up to form new crust. Rifting creates undersea valleys.
What happens at a destructive plate margin ?
Hydration melting happens in subduction zone- water involved lowers melting temp. Parallel to plate, unstable mantle material forces itself to the surface. In the Benioff zone, crust rocks melt and chemical reactions occur at the high temps and pressures. Slab pull pulls the oceanic plate down.
What happens at a collision plate boundary ?
Faulting at connection of 2 plates leads to v wide, mostly shallow, earthquake zone. Slab pull pills down the continental plate. Both plates are the same densities, leading to fold mountains.
what are jokulhaups ?
A heavy and sudden flood caused when the heat of a volcanos eruption melts the snow and ice in a glacier.
What is the elastic rebound theory ?
The process of strain, stress, and failure, in a locked fault.
What is a locked fault ? And example
A fault that is not slipping because the frictional resistance of the fault s greater than the shear stress across the fault. e.g. The 2004 Indian Ocean tsunami was the result of a mega thrust locked fault.
on a general level, what do earthquake waves cause?
secondary hazards (liquefaction and landslides)
what are the primary hazards of volcanoes?