hazards Flashcards
what are the main physical layers of the earth
lithosphere
asthenosphere
lower mantle
outer and inner core
what is the crust mainly made up of
silicates
what makes up the lithosphere
crust and solid mantle
whats the mantle mainly made up of
silicates but contains magnesium and iron
what is the core mainly made up of
metal
what is isostasy
the rising and settling of a part of the earths lithosphere
define what a plate is
a piece of the earths lithosphere that sits on top of the heavier asthenosphere
describe basal drag
higher temps on earths core generates zones of hotter magma which upwell
cooler denser material sinks down creating a continuous circulatory motion
pulling crust apart by basal drag
describe ridge push
fresh magma up wells at mid ocean ridges forming new young , ocean lithosphere pushing rock up and out
oceanic core cools and thickens and is pushed downhill with new magma emerging
describe slab pull
when cold, dense plates sink into the mantle causing the whole thing to be forced down due to weight
due to gravity
what is continental fit
idea that countries fit together
what is continental drift
theory that suggests that the continents have moved
how has similar rock types provided evidence for continental drift
rocks of same age and type displaying same formations discovered in Europe, North America and Africa
how has mountains provided evidence for continental drift
old mountain belt refinance found between 450 to 400 million yrs ago
Appalachian mountain range found in US and Greenland
how has glacial deposits proved evidence for continental drift
deposits formed during Permo-carboniferous era are found in Antartica, Africa, South America suggesting continents reassembled in the South Pole
glacial striations - scratches on bedrock made by rocks embedded in ice show direction of glacier suggest ice flowed from a single point
what is palaeomagnetism and what impact do they have on proving plate tectonics
when lava erupts on ocean floor iron-rich minerals are aligned with magnetic field of earth, this cools recording earths polarity this resets every 400,000 years
bands of normal and reverse polarity are mirrored each side of mid Atlantic ridge suggesting new rock added each Side and width creates a pattern
what impact does ocean surveys have on proving plate tectonics
they help provide a detailed picture of the ocean bottom
help geoscientists identify mountainous features where new plates form and deep ocean trenches descend
what was noticed about the age of the sea floor to help prove plate tectonics
shown to be very young ages for rock locations close to ridges and old for ocean floors near continental masses. older rocks were cooler and denser
explain what a mid Atlantic ridge is
where oceanic lithosphere is drawn apart
upwelling mantle lifts oceanic lithosphere upwards
what is decompression melting
when pressure is released rock that was previously held as a solid due to pressure liquifies
why do volcanoes form at divergent plate boundaries
much higher volumes of basaltic magma are produced forming an island such as island
what kinds of volcanoes do we get at divergent plate boundaries
- sheild volcanoes
what kind of eruptions do we get at divergent plate boundaries
- icelandic and Hawaiian
what is a transform fault
where two ridges are broken up and slide past each other horizontally
what is pillow lava
when lava enters water rapidly and its surface chills rapidly forming a flexible rind around molten interior
