Seafloor spreading & plate tectonics Flashcards
who was Harry Hess
Harry Hammond Hess was an American geologist who proposed a theory for why the continental drift of tectonic plates occurred.
how did he get interested in geology
He became interested in geology during his time as a Naval officer during in WWII.
what are mid ocean ridges
active underwater volcanoes.
what is seafloor spreading (short)
New oceanic crust (rock) is added to the ocean floor, making it grow and spread apart.
what are the steps of seafloor spreading
- Magma erupts and pushes the older rocks
away, forming new rock crust. - Over time, theseafloorspreads outon
either side of themid-ocean ridgethat is
producing it. - The oldest rocks at the far edge get pushed
down into the mantle and recycled.
what did Harry Hess discover underwater
Hess found that the seafloor is actually a weird and wonderful place!
(trenches, volcanoes, mountains and
what was the expectations about the seafloor
it was flat
what was the reality about the seafloor
they covered in all sort of things
what are the three evidences of seafloor spreading
pillow shaped rocks
magnetic striping
age of rock samples
def pillow shaped rocks
Pillow-shaped rocks can be found along the mid-ocean ridge, showing that molten material has bubbled up repeatedly from cracks along the center of the mid-ocean ridge.
def magnetic striping
Magma contains magnetite (iron ore) which has magnetic properties. As the magma at mid-ocean ridges welled up, cooled then solidified, the magnetite lined up with the Earth’s magnetic field.
what is the theory of plate tectonics
Large-scale movement of continental plates that cause the formation of mountains, volcanoes and earthquakes.
what are the seven major tectonic plates
north american
south american
african
australian
antartic
pacific
eurasion
what are the seven minor tectonic plates
nazca
cocos
carribean
indian
arabic
smali
philliphene
scotian
what’s in the pacific plate
pacific ocean
