Restless Earth Flashcards
What is the Asthenosphere?
The sticky, dense layer of rock in the mantle
What is the Lithosphere?
The crust and the solid top layer of the mantle
What is the core made of?
Iron and Nickel
Describe the differences between Oceanic crust and Continental crust.
Oceanic - made of Basalt, underneath water
Continental - made of Granite, underneath land
Describe the differences between Granitic rock and Basaltic rock.
Granite - large crystals, formed by magma cooling slowly, orange-brown colour, makes continental crust
Basalt - no visible crystals, occurs in lava flows and sheets, black-grey colour, makes oceanic crust
Explain how tectonic plates move.
Earth core gives off heat causing convection currents or movement of magma in the Asthenosphere causing the crust sitting on top of it to move and the tectonic plates move too.
Outline the key features of the Earths structure.
Core - inner core (solid), outer core (liquid)
Mantle - above core, low density, upper solid, lower liquid
Crust - solid, low density, tectonic plates - oceanic (more dense, basaltic rock, below water) continental (less dense,thick, granitic rock, below land)
Name all 12 tectonic plates.
Pacific, Antarctic, Philippines, Indo-Australian, North-American, Nazca, South-American, Caribbean, African, Eurasian, Iranian, Arabian
Name the 4 types of plate boundaries.
Constructive - Plates pull away from each other
Destructive - Plate pushes under other
Collision - Plates push into each other
Conservative - Plates slide past each other
Explain what happens at a Constructive plate boundary.
Convection currents cause oceanic plates move away from each other
Basaltic material and hot magma rises through gap
Mid ocean mountain range formed
Magma continues to rise to form a volcanic island
Explain what happens at a Destructive plate boundary.
Convection currents move plates
Oceanic plate subducts under less dense continental plate
Forms a fold mountain and ocean trench
Magma rises through weaknesses forming volcanoes
Explain what happens at a Collision plate boundary.
Convection currents cause two continental plates to move towards each other
Same density so no subduction
Crust buckles to form fold mountains
Explain what happens at a Conservative plate boundary.
Convection currents cause plates to slide past each other
No subduction or magma therefore crust neither created or destroyed Stress builds up in crustal rocks from friction which causes earthquakes when released
Define an earthquake.
The shaking of the Earth’s crust caused by rock movement.
Define a volcano.
A cone shaped hill or mountain formed by the lava and ash from eruptions.
Describe the 3 types of volcanoes.
Extinct - not erupted for 1000 years, shape worn away by wind and rain
Dormant (sleeping) - not erupted for years or even centuries but still seeps gas sometimes
Active - erupted recently and likely to erupt again
What is the hot spot theory?
When hot magma rises to the surface pushing through a continental plate crossing over it, forming chains of volcanoes over thousands of years.
Describe the features of a shield volcano.
Mainly formed by basaltic magma, Low, wide cone, large, gentle slope (lava drizzles/slides down)
Describe the features of a composite volcano.
Made of andesitic lavas, steep sided, bumpy cone, layers of lava and ash.
What are pyroclastics?
Pieces of ash and rock debris or material destroyed in explosive eruptions.
Describe the features of basaltic magma.
High temp, low silica/gas, fluid lava flow, little explosive activity, found in shield volcanoes on conservative plate margins
Describe the features of andesitic magma
Low temp, more silica than basaltic, dissolves gases, less fluid, more likely to explode when reaches surface, found in composite volcanoes at destructive plate margins.
Describe the features of granitic magma
Low temp, High silica, viscous, sticky, gets stuck before reaches surface so not found in volcanoes.
How is Ash formed?
From material destroyed in explosive volcanic eruptions.
