Geological Processes • Tectonics • Rocks bend and break (folding and faulting). • Volcanism • Rocks melt and explode. • Erosion and surface processes • Surfaces flatten out: mountains crumble and holes are filled in. • Mass wasting (gravity action) • Wind action • Water action • Impact Cratering (external) • Bodies from space hit the ground, making a hole.
Tectonics -Folding • When rocks are squashed they will compress and bend away from the direction of maximum pressure
Wrinkle Ridges on the Moon • Cooling rocks contract, the shrinkage causes folding and ridges form
Tectonics -Faulting • Extension Faults -crust moves apart, makes a larger area. • Compression Faults -crust moves together, makes smaller area. • Strike-slip Faults -crust moves sideways, no gain or loss of area
Volcanism Rocks melt and explode
Volcanic Processes • Rocks melt and explode. • 2 components: lava, gasses • Lavas - variable viscosity,depending on chemistry • Low viscosity range of viscosity High viscosity (runny lava) (gooey, sticky lava) Low gas content High gas Result: Result: Low broad shapes range of volcanoes Tall cone shapes Volcanic Shield Cinder Stratovolcanoes Floods Volcanoes cones
Olympus MonsMartian Shield Volcano • Note the broad shield shape and the central cauldera
Mt St Helens More tytpical eruption Oct 1st & 5th 2004
Many cities are built below stratovolcanoes e.g Seattle and Mt Rainier
This eruption from Mt Etna in 1983 shows lava flows engulfing the tourist facility.
Soufrière Hills, Monserrat 1995 Southern half of island evacuated and capital city lost
Alternative Materials: Sulfur • Spacecraft observe live sulfur volcanoes on Io
Erosion and Surface Processes • Surfaces flatten out: mountains crumble and holes are filled in. The processes that carry out erosion each show characteristic patterns: • Mass wasting (gravity action)- land slides • Wind action- sand dunes, wind streaks • Water action- river channels, ocean shores, glacial erosion
Sand Dunes in the Sahara (imaged by the Space Shuttle)
Sand Dunes in the Namib (imaged by the Space Shuttle)
Cape Cod, Earth • Material is carried to the oceans and dumped. • Gains are ground up by pounding waves. • THIS IS UNIQUE TO EARTH
Impact Cratering • Bodies from space hit the ground, making a hole. (the only external process -it comes to the planet from the outside) • The size of the hole depends on the energy of the impact. • A small, slow-moving, ice-ball makes a small hole. • A massive, fast moving, rock makes a large hole.