introducing planet earth Flashcards
the solar system
a group of celestial bodies including earth orbiting around and gravitationally bound by the star known as the sun
Name the 8 planets
1) mercury
2) venus
3) earth
4) Mars
5) jupiter
6) saturn
7) uranus
8) neptune
1-4 - terrestial planets
5-8- icy planets
name the 3 dwarf planets
Pluto , Eris , ceres
define asteroids
rocky, metallic objects that orbit around the sun in the asteroid belt between mars and Juoiter
define comets
small, icy bodies that orbit around the sun
meteoroids
small bodies that travel through space - stony and metallic - smaller than ase
name earth’s inner structure
the crust
the mantle
outer core
inner core
name the characteristics of the crust
the thinnest layer
comprised of 2 types of crusts;
1) continental crust
2) oceanic crust
the continental crust - solid layer of rocks that make up the continents and continental shelves (shallow seabed close to shore )
the oceanic crust -part of Earth’s crust that forms the ocean bed
most common elements ; oxygen , silicone , aluminium ,
the continental crust - older , lighter ,cannot sink and is permanent
the oceanic crust ; carries water ; younger , heavier , can sink - constantly being destroyed and replaced
Characteristics of the mantle ;
a thick layer . Made up of oxides of silicone and magnesium . Earth’s internal heat is found here
the mantle can be divided into 2 ;
outer mantle ; consists of a solid layer below which is a layer of sow flowing molten rock in a plastic state
inner mantle - solid because of high pressures
characteristics of the core ;
outer core ; a dense liquid layer - composed mainly of molten iron and nickel - controls Earth’s magnetic fields
Inner core - solid mass - nickel and iron alloy
the lithosphere
includes the crust and the rigid upper part of the mantle -
the mohorovicic discontinuity - separation between crust and upper mantle-
strongest layer because it is relatively cool since it is so close to the surface
not a continuous layer but formed of plates
- 8 large plates that move constantly supported by the flowing asthenosphere
the asthenosphere
part of the upper mantle that exhibits plastic properties -located below lithosphere
how many large plates and how do they move ?
1) six large plates
2) They move horizontally and vertically - continuous motion driven by the convention currents
plate tectonic theory
explains the movement of earth’s crust throughout the geologic time producing continental drift that has resulted in present-day positions of the continents . it also explains the locations of mountain building, earthquakes and volcanoes
the current continental and oceanic plates ;
The Eurasian plate, Australian Indian plate , philippine plate, Juan De Fuca plate, Nazca plate , Cocos plate , North American plate, caribbean Plate, south american plate , African plate , arabian plate , antarctic plate and scotia plate
plate boundaries -
edges of lithospheric crust where plates interact with other plates hence earthquakes volcanic activity
also mountain building and ocean ridges formation occur here
3 types of plate boundaries ;
divergent boundaries
convergent boundaries
transform boundaries
divergent boundaries- mid -ocean ridges
when 2 plates separate , the space created between them is filled by magma which solidifies to form basalt - new rock is formed
mid-ocean ridges are underwater mountain ranges formed as magma frim asthenosphere is forced through a crack in the oceanic crust and cools . this causes new oceanic crust - sea - floor spreading
example - MId-atlantic ridge - north american plate and eurasian plate
sea-floor spreading
movement of 2 oceanic plates away from each other -formation of new oceanic crust - zone of divergence
a divergent boundary involving two continental crusts
for example - african plate that is diverging from the arabian plate giving rise to the red sea
convergent boundaries
occur at collision zones where plates are moving towards one another - volcanism and earthquakes
name the 3 types of collisions
1) oceanic plate and continental plate
2) two oceanic plates
3) two continental plates
oceanic plate and continental plate collision
two plates push against each other until the denser plate (oceanic plate) is forced into the mantle - generate earthquake activity . As the ocean plate sinks into the mantle , parts of it may melt and form magma. This magma travels upward and encounters the overlying continental crust forming a volcano .
what happens when a plate with oceanic crust is forced against another plate with oceanic or continental crust
a subduction zone occurs which is forced into the asthenosphere- the subducting slap enters at an angle which gives rise to a trench
what is a significant characteristic of the convergent boundaries
when the 2 plates collide , the sediments situated between them are upthrust to form a mountain range and orogery (mountain range
Two oceanic plates
one may be pushed under the other and magma from mantle rises ,forming volcanoes in vicinity
two continental plates
when 2 continental plates collide ,mountain ranges are created as the colliding crust is compressed and pushed upwards- the Himalayan mountain range
conservative boundaries
they don’t involve the creation or destruction of plate material . The two plates slide past eachother (same or opposite direction )
Earthquakes
The shaking and vibration of the Earth’s crust due to the movement of earth’s plate (sudden release of accumulated strain )
friction prevents rock on both sides of a fault form slipping , but when the force is acting on the rock exceeds the frictional resistance the sides move suddenly
why do the plates move?
they move because of convention currents as a result of the very high temperature in the inner core
what happens when the plates pass past each other?
stress is created , the crust will break forming a fault -
when the break occurs , the stress is released as energy that moves through the earth in the form of a seismic wave
Earthquakes can occur at all boundaries especially at convergent and conservative boundaries
where are earthquakes most common
circum pacific seismic belt - ring of fire
the Mediterranean and trans-Atlantic belt which extends froms
the focus
the point below earth’s surface at which the earthquake originates (point of initial movement)
epicentre -
the point on the surface directly above the focus - most severe damage
what can an earthquake be measured by ?
intensity and magnitude
intensity
intensity assesses the strength of shaking produced by an earthquake at a certain location - determined by effects on people , building and infrastructure and natural environment - can be subjective and intensity scales are useless in inhabited areas- Mercalli scale
Magnitude
calculates the amount of energy release at the source of earthquakes -seismographs - measure size of seismic waves-ritcher scale - logarithmic scale -
primary effects of an earthquake
caused directly by the ground shaking and breaking in more severe cases - severe damage to building and infrastructure
secondary effects
consequences of primary effects - can cause more loss of life than primary effects - landslide fires , floods etc
Tsunami -
a particular secondary effect - created by sudden displacement and underwater volcanic eruptions - they star as shallow waves with a long wavelength - they move at very fast speeds from epicentre. Close to shore the waves slow down and rapidly gain height
