Living With Tectonic Hazards KQ1 Flashcards
Describe the features of the core.
The core is composed mostly of iron and nickel. It is divided into a solid inner core 1200km thick and a liquid outer core which is about 2100 km thick. The temperature of the core is between 3000C and 6000C.
Describe the features of the mantle.
The mantle consists of mostly solid rock but flows under high temperature and pressure and is around 2900km 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 and easily deformed. The temperature is between 800C and 3000C
Describe the features of the crust.
The crust is the outermost layer on which we live. It is made out of two types of crust, oceanic and continental. The oceanic crust is found beneath oceans, is very thin, 5-8km thick, and is denser than continental crust. Continental crust is found beneath the continents, is very thick, 30-70km thick and less dense than oceanic crust. The thickness of the crust ranges from a few km to more than 70km.
How does slab-pull force cause the movement of tectonic plates?
When an oceanic plate subducts under a less dense plate, it pulls the rest of the plate along. The subduction plate drives the downward-moving portion of convection currents. While the mantle material away from the subduction zone drives the rising portion of convection currents.
Why do tectonic plates move?
Tectonic plates move due to convection currents within the mantle. The core heats material in the mantle which causes convection currents in the mantle material. The mantle expands, rises and spreads out beneath the plates which are dragged along and move away from each other. Subsequently, the mantle cools and sinks, pulling the plates along so plates move towards each other. The sinking mantle material heats up again as it nears the core and the whole process repeats.
Describe the process when convergent plate movement occur between 2 oceanic plates.
The denser plate will subduct beneath the other plate and a deep ocean trench is formed at the subduction zone. The mantle above the subducted plate melts forming magma which rises through faults in the crust forming undersea volcanoes. Eventually the volcanoes may rise above sea level to form volcanic islands and earthquakes may also occur at the boundary between plates. An example of this are the Pacific plate and Philippine plate.
Describe the process when divergent plate movements occurs between 2 oceanic plates.
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 and at various points along the ridge, magma builds up above the ocean to form volcanic islands. Examples of this are the North American Plate and Eurasian Plate.
State the features and phenomena with examples that is resulted from divergent plate movements between 2 oceanic plates.
When divergent plate movement occurs, mid-oceanic ridges, volcanoes and volcanic islands are created. Examples where this occurs are the Mid-Atlantic Ridge, Askja, Iceland and Iceland respectively.
Describe the process when divergent plate movement occurs between 2 continental plates.
Fractures form at the divergent plate boundary and the land between the continental plates sink forming a linear depression. This is called a rift valley. Examples of this occurring are the Somalian boundary of African plate and Nubian boundary of the African plate.
State the features and phenomena with examples that is resulted from divergent plate movements between 2 continental plates.
When divergent plate movements occur between 2 continental plates, rift valleys, block mountains, volcanoes and earthquakes are created. Examples of these are the Great East African Rift Valley and Mt. Kilimanjaro.
Describe the process when convergent plate movement occurs between 2 oceanic plates.
When two oceanic plates converge, the denser plate will subduct beneath the other plate and a deep ocean trench is formed at the subduction zone. The mantle above the subducted plate melts forming magma which rises through faults in the crust forming undersea volcanoes. Eventually, the volcanoes may rise above sea level to form volcanic islands and earthquakes may also occur at the boundary between the plates. Examples of this are the Pacific plate and Phillippine plate.
State the features and phenomena with examples that is resulted from convergent plate movements between 2 oceanic plates.
When convergent plate movement occurs between 2 oceanic plates, features and phenomena that are created as a result are oceanic trenches, Island Arcs, volcanoes and Earthquakes. Examples of these are the Mariana Trench, Marianas Islands and Asuncion respectively.
Describe the process when convergent plate movement occurs between 2 continental plates.
Plates made largely of continental crust may collide with other plates made 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. Examples of this are the Indian plate and Eurasian plate.
State the features and phenomena with examples that is resulted from convergent plate movements between 2 continental plates.
When convergent plate movement occurs between 2 continental plates, features and phenomena that are created as a result are fold mountains and earthquakes. An examples of this are the Himalayan mountains.
Describe the process when convergent plate movement occurs between an oceanic and continental plate.
The denser oceanic plate subducts beneath the continental plate and a deep ocean trench is formed at the subduction zone. The mantle above the subducted plate melts forming magma which rises through the crust forming volcanoes. The crust of the continental plate is compressed and folds upwards or sideways which forms fold mountains. Earthquakes may also occur at the boundary between the plates. Examples of this are the Nazca plate and South American plate.
