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Tectonic processes and hazards - Coggle Diagram
Tectonic processes and hazards
Earth Structure
Crust- it is composed of a variety of igneous, sedimentary and metamorphic rocks. It occupies less than 1% of Earths volume
Lithosphere- it is the rocky outer part of the Earth, it is made of the brittle crust and the top part of the upper mantle. It is the coolest, most rigid part of the Earth. It is around 100km thick
Asthenosphere- Highly viscous and mechanically weak part of the upper mantle. It lies below the lithosphere at depths of between 100 and 200 Km.
Mesosphere (in geology)- This refers to the part of the Earths mantle between the Asthenosphere and the outer core. It is roughly 2,900Km (1,802 miles) thick, and makes up 84% of Earths volume
Outer core- is a fluid layer composed of mostly iron and nickel and is 2,400Km (1,500 miles) thick.
Inner core- is a hot dense ball mostly made of iron and has a radius of about 1,220Km (758 miles). The temperature within the inner core is about 5,200° Celcius.
Plate Boundaries
Convergent (Destructive)
This is where two different tectonic plates move toward each other, if the two plates are of equal density, they will start to form mountains.
If the two plates are of different densities, the lighter one will start to subduct underneath the heavier more dense plate.
An example of this is on the Andes mountain range in South America, this is where the Nazca plate subduct underneath the South American plate
Divergent (Constructive)
This is where two different plates move away from each other, leaving room for magma to be pushed up by the mantle, and form new land within this gap.
Two examples of this type of boundary in real life are the mid Atlantic ridge, and the South African Rift Valley.
Transform
This is where the two plates Slide next to each other but at different speeds, an example of this is the San Andreas Fault.
Volcano types
Active volcano
Is a volcano that is still erupting
Dormant volcano
Is a volcano that is 'sleeping', not erupting regularly
Extinct volcano
Is a volcano that is no longer erupting
Shield volcano
Are relatively low, with gentle sloping sides.
Composite volcano
Are built up of layers of alternating lava flow, ash and blocks of unmelted stone.
Cinder volcano
Simple volcano with a bowl shaped crater at the summit, typically only grow to about a thousand feet.
Key words for volcanoes
Explosive eruptions
Caused by the build up of pressure within a volcano, ejects acid lava, gases, ash, and rock fragments.
Occur where cooler, more viscous magmas (such as andesite) reach the surface. dissolved gases cannot escape easily and pressure begins to build until gas explosions blast rock and lava fragments into the air
Effusive eruptions
Occur when hot, (120°) runny basalt magmas reach the surface
Dissolved gases can escape easily as the magma erupts, forming lava that flows downhill quite easily
Lahar
A Lamar is a volcanic mud flow
Pyroclastic flow
A pyroclastic flow is a superheated mixture of hot steam, rock, ash and dust. It is extremely fast moving and can reach temperatures of 400°C.
Hotspot
A hotspot is an area of the Earth that exists above a mantle plume. hotspot volcanos occur far from plate boundaries because the Earths plate boundaries move, but the hotspot does not.
This process can create a chain of volcanoes on top of the Earth's surface. An example of this is the chain of volcanoes on Hawaii
Key things to remember
Continental plate
Is a slab of the Earth's crust that is thick, it holds the continents and cannot me made or destroyed.
Oceanic plate
is a slab of the Earth's crust that is thin, it holds the Earths oceans and it can be made or destroyed.
Subduction zone
Found on a destructive plate margin, and is where the oceanic plate gets Bent under (Subducting) the continental plate. It is forced down to the mantle where it melts.
Convection currents
These are what move the tectonic plates. as heat rises in the Earths mantle it moves upwards, and as it reaches the crust it moves to one side, until it cools where it goes back down. this current of hot mantle rising and cool mantle falling is called a convection current.
A convection current is kind of like a conveyor belt as it is moving the Earths plate boundaries.