seafloor spreading Flashcards
(59 cards)
The mechanism that operates along the oceanic ridge system to create new seafloor.
seafloor spreading
The mechanism that operates along the oceanic ridge system to create new _____.
seafloor
Typical rates of spreading average around ______, roughly the same rate at which human fingernails grow.
5 cm/year (2 inches)
Comparatively slow spreading rates of ____ are found along the Mid-Atlantic Ridge, whereas spreading rates exceeding ______ per year have been measured along sections of the East Pacific Rise.
2 cm/year; 15 cm/year (6 inches)
The seafloor has a large _____ running through it. Deep trenches are found ___ from the ridges.
mountain range; far
The _________ of the seafloor changes.
magnetic polarity
The center of the ridge is of ______.
normal polarity
Stripes of normal and reverse polarity are found ______ on both sides of the ridge.
symmetrical
The rocks ____ to the ocean ridge were _____ than the rocks found further from the ridge.
closest; younger
This means that new rocks are formed at the ____ and push the older rocks away from the ridge based on the core sample collected from 1968, a drilling ship called the Glomar Challenger.
ridges
The seafloor has a large mountain range running through it. Deep trenches are found far from the ridges.
evidence of seafloor spreading
The magnetic polarity of the seafloor changes. The center of the ridge is of normal polarity. Stripes of normal and reverse polarity are found symmetrical on both sides of the ridge.
evidence of seafloor spreading
The rocks closest to the ocean ridge were younger than the rocks found further from the ridge. This means that new rocks are formed at the ridges and push the older rocks away from the ridge based on the core sample collected from 1968, a drilling ship called the Glomar Challenger.
evidence of seafloor spreading
The ____ seafloor is much _____than the oldest continent.
oldest; younger
The oldest ocean floor rocks ever found are ___ million years old.
180
This proves that ocean floor is being ____ therefore all ocean floor rocks are ____ compared to the age of Earth.
destroyed; young
Rocks shaped like pillows (_____) shown that molten material has erupted again and again from cracks along the mid- ocean ridge and cooled quickly.
rock pillows
The oldest seafloor is much younger than the oldest continent. The oldest ocean floor rocks ever found are 180 million years old. Remember the Earth is 4.6 billion years old. This proves that ocean floor is being destroyed therefore all ocean floor rocks are young compared to the age of Earth.
evidence of seafloor spreading
Rocks shaped like pillows (rock pillows) shown that molten material has erupted again and again from cracks along the mid- ocean ridge and cooled quickly
evidence of seafloor spreading
Stripes in the seafloor. When magma cools, the iron cools into the mineral magnetite. It lines up parallel to the Earth’s present magnetic field. This iron is like compass needles, pointing north. So, when the rock hardens, a record of the Earth’s magnetic field at that time is locked in stone.
evidence of seafloor spreading
who pioneered the seafloor spreading theory
Harry Hess (1906-1969)
Harry Hess is a Former ____ Professor at ____ University
Geology; Princeton
Harry Hess was also a Head of Princeton’s _______
Geology Department
He was also the ____ of the Space Science Board of the National Academy of Sciences.
Chairman
