The Geosphere (Solid Earth)

Longitudinal waves P-waves. Like sound waves or acoustic wave.

S-Waves or shear waves travel slower than P-waves. The motionOf the wave disturbance is perpendicular to the wave’s motion.

If one know the speeds of the P-wave and S-wave (Vp and Vs) , then the difference between P-wave arrival (Tp) and S (Ts)wave arrival can be used to figure out the distance to the Earth quakes.

D= Vp Tp

D= Vs Ts

PS

PS

VV

TTD

11

)(

3 stations need to locate the focus of the Earth quake.

http://www.tectonics.caltech.edu/outreach/animations/mase/mase_tomography.html

Earth’s Radius 6400 kmDepth to inner core 5000 kmDepth to outer core 3000 kmDepth to mantle 10 to 50 km (oceanic crust 10 km Continental crust 50 km)

The lithosphere is hard / brittle

The asthenosphere can deform likestiff putty.

Oceanic crust is relatively young (80 million years) whereas continental crust can be billions of year old.

Earth Radius 6400 kmDepth to inner core 5000 kmDepth to outer core 3000 kmDepth to lower 1000 km Mantle

There are approximately 12 lithospheric plates on Earth’s surface. Most scientists believe that convection within Earth’s lower and upper Mantle is the major driving force linked to plate motion. Convection is driven my temperature differences/density differences and gravity.

Juan de Fuca plate. Spreading and subductionMt St Helens is part of the Cascade Arc Volcanoes

Hot spot volcanoesHawaiian Islands

Hot Spots and Mantle plumes reaching the surface. Hot spots tend to be relatively stationary. As an oceanic plate moves over a hot spot new islands can be formed. Most think that the hawiian islands are a result of motion over a hot spot.

Plate motion at trenches can be up to 10 to 12 cm year.

Continental crust is very old because it does not get recycled frequently. Oceanic crust is typically 100 million years old on average (fairly young). Oceanic crust is continually recycled.