hazardous earth - tectonic plates Flashcards
define lithosphere
the upper most layer of the earth - the top of the mantle and the crust
define asthenosphere
lower part of the earth’s mantle
how hot is the inner core
6000°C
how hot is the outer core
5000°C
how hot is the mantle
3800°C
how thick is the oceanic crust (km)
6-8 km
what is the oceanic crust made of
basalt
how thick is the continental crust (km)
30-50 km
what is the continental crust made of
granite
is the oceanic or continental crust denser
the oceanic crust is denser
which type of crust can be destroyed (continental or oceanic)
oceanic can be destroyed when two techtonic plates meet
what makes the core so hot
radioactive decay of some elements eg
uranium
what is the magnetosphere
a huge invisible magnetic field that surrounds the earth, protecting us from harmful radiation from space
what part of the earth produces the earth’s magnetic field
the outer core
what is pangea and how long ago did it exist
250 million years ago, the continents were once all joined together as one large supercontinent
give two points as to how we know that pangea existed
- there are the same fossils in different continents
- some continents appear to fit together
define plate boundary
where two plates meet
conservative plates - direction
- features/ hazards
- alongside each other or against each other
- destructive earthquakes up to 8.5. small earth tremors almost daily
divergent - direction
- features/ hazards
- away from each other
- small earthquakes 5-6 magnitude. not very dangerous volcanoes
convergent - direction
- features/ hazards
- towards eachother
- very destructive earthquakes up to 9.5. very destructive volcanoes. tsunamis can form
collision - direction
- features/ hazards
- toward eachother
- destructive earthquakes 9. landslides. volcanoes are very rare
what are destructive plate boundaries
it’s another name for convergent plate boundaries
compare a convergent and collision plate boundary (4)
• both go in the same direction (towards each other)
• both produce extremely destructive earthquakes
• convergent have 1 continental and 1 oceanic but collision have 2 continental
• only convergent can form tsunamis
define hotspot and give an example of one
where a rising plume of magma breaks through the earth’s surface in the middle of a plate. this causes a volcano. eh hawaiii
define volcano
an opening or vent in the earth’s surface through which molten material erupts and solidifies as lava
where are composite volcanoes found
convergent boundaries
what are composite volcanoes made of and what is the lava Iike
alternating layers of ash and lava
andesitic, thick, sticky lava which doesn’t flow very far before solidifying
what are eruptions like for composite volcanoes and why
they are explosive due to more silica and more gases
what are pyroclastic flows and what kind of volcano are they caused by
fast moving current of hot gas and volcanic matter. found at composite volcanoes
where are shield volcanoes found
divergent plate boundaries
what are shield volcanoes made of and what is the lava Iike
formed by layers of basaltic runny lava which can flow long distances before solidifying so the volcano is low with gentle sloping slides
what are explosions like for shield volcanoes
frequent but gentle eruptions produced under low pressure
explain the differences between shield and composite volcanoes (4)
• shield are formed at divergent boundaries. composite are formed at convergent
• shield are broad, gently sloping. composite are tall and thin
• shield have frequent, gentle eruptions. composite have explosive eruptions
• shield formed from layers of solid lava. composite formed form layers of lava and ash layers
two ways that volcanoes can be predicted
- thermal imaging
- seismometer
define earthquake
a vibration of the earth’s crust. tectonic plates try to push past each other, pressure is built up which is suddenly released
what is magnitude measured with?
a seismometer
what does it mean that the Richter scale is logarithmic
a magnitude of 5.0 is 10 times more powerful than 4.0
