science study guide

what were thres peices of evidence that wegener used to support his hypothesis of continential drift

1. matching rockforms

2. fossil evidence

3. glacier evidence

what did early cartographers realize, which supported continential drift

the continents looked like they fit together like a puzzle

why wasn’t wegeners hypothesis supported at first

because he didn’t have evidence of how the continents moved

who was Harry hess

whe was a geoglogists who helped prove the spreading of the seafloor by discovering deep underwater trenches and mid altlantic ridges

how did sonar help support the theory of the seafloor spreading

they would map the seafloor, showing deep seafloor trenches and ridges

what two pieces of evidence support the theory of seafloor spreading

magnetic stripes and the age of oceanic rocks

prior to the mid 1900s what did people think the seafloor looked like

people thought that the seafloor was completely flat

what is the difference between an ocean ridge and an ocean trench

a trench is a deep split in the seafloor and ridges are underwater mountain chains

what type of boundary does new crust form at? what type of plate boundary does old crust get destroyed at?

a divergant boundary forms new curst and at a convergent boundary old crust gets destroyed

compare and contrast continential and oceanic crust

continential crust is older, while oceanic crust is denser

describe what happens at an oceanic continential plate boundary

oceanic plate subducts beneath continential plate and forms and deep sea trench and volcanic mountains

describe how the Himalayan mountains formed

the Indian austrailian plate subducted under the Eurasian plate

what forms at a transform boundary

faults and earthquakes

what is the formula for density? if a rock has a mass of 85mg and a volume of 32ml, what is its density

d=m/v it would be 2.7g

what are volcanic hot spots

unusually hot regions of earth’s mantle where magma breaks through the earth’s crust

explain how the hawaiian islands were formed

they were formed by stationary hotspots over the pacific plate, that moved causing magma to break through Earth's crust

what is the difference between convergant and divergant volcanism

convergant - happens after subduction, causes magma to rise

divergant - hot mantle rises when rocks are pulling apart

decribe the motion of a p wave

move in any direction, fastest wave, they are felt on earth but absorbed and refracted at the core boundary

describe the motion of an s wave

move in a n up and down motion, travel at a medium speed, can travel through all layers of the earth

what seismic wave is the most destructive, why?

surface waves are the most destructive because they create larger waves and only travel through the crust, where buildings sit

what is the difference between the focus and the epicenter

focus - point where body waves originate

epicenter - point on earths surface above the focus, surface waves originate here