Tectonic Hazards Gateway 1 Flashcards
How is the Core made up of.
The core is mostly iron and nickel and it is divided between the solid inner core (1,200km thick) and the liquid outer core (2,100km thick). The temperature of the core is mostly 3000 to 5000 degree Celsius.
What is the Mantle?
the Mantle is outside of the Core. It is mostly solid rock but flows under high temperature and pressure. 2,900km thick, it is divided into the upper mantle and the lower mantle. The Upper mantle is a layer of solid rock and the asthenosphere where the rocks are close to melting point easily deformed. The temperature is between 800 to 3000 degree Celsius.
What is the Crust?
The Crust is the outermost layer on which we live. It is made of two types of crust, oceanic and continental. Oceanic crust is found beneath oceans, is very thin ( 5-8km thick) and denser than continental crust. Continental crust is found beneath continents, is very thick (30-60km thick) and less dense than oceanic crust. Thickness ranges from a few km to more than 70km.
Explain the movement of Tectonic Plates.
Tectonic plates move due to convection currents within the mantle. The core heats material in the mantle. This causes convection currents in the mantle material. Mantle expands, rises and spreads beneath the plates. Plates are then dragged along and move away from each other. Subsequently, the mantle cools and sinks.. The sinking mantle material heat up again as it nears the core and the whole process repeats. Tectonic plates also move due to Slab-Pull force. This occurs when an oceanic plate (denser) subducts under a less dense plate and pulls the rest of the oceanic plate along.
Divergent plate Movements. Oceanic-Oceanic.
It is when Magma rises from the mantle at the zone of divergence to fill the gap between the plates as they move apart. This cools and solidifies to form a ridge of new ocean floor called a mid-oceanic-ridge. This process is called sea-floor spreading. At various points along the ridge, magma builds up above the ocean to form volcanic islands. This forms Mid-oceanic ridge, volcanoes and volcanic islands
Divergent plate Movements. Continental-Continental.
It is when fractures form at the divergent plate boundary. The land between the continental plates sink forming a linear depression. It is called a rift valley. This forms Rift valleys and block mountains, volcanoes and earthquakes.
Convergent Plate Movements. Oceanic-Oceanic.
This happens when two oceanic plates converge, the denser plate will subduct beneath the other plate. A deep ocean trench is formed at the subduction zone. The mantle above the subducted plates melts forming magma. This magma rises through faults in the crust forming undersea volcanoes. Eventually the volcanoes may rise above sea level to form volcanic islands. Earthquakes may also occur at the boundary between plates.
Convergent plate Movements. Continental-Continental
Plates made largely of continental crust may collide with other plates made of largely of continental crust. However, both plates have similar densities and hence, resist subduction. Instead, the plates break, slide along fractures in the crust and fold, forming fold mountains and causing earthquakes.
Convergent plate Movements. Oceanic-Continental
The denser oceanic plate subducts beneath the continental plate. A deep ocean trench is formed at the subduction zone. The mantle above the subducted plate melts forming magma, this magma then rise through the curst forming volcanoes. The crust of the continental plate is compressed and fold upwards or sideways. This forms fold mountains. Earthquakes may also occur at the boundary between the plates.
Transform Plate Boundaries. Continental-Continental or Oceanic-Oceanic.
Plates slide past each other. As they do so, tremendous stress builds up. This stress is eventually released, often as a violent earthquake.
