Show:
Seafloor Spreading
Machines/Technology
Magnetic Polarity
Mid Ocean Ridge
Magnetic Stripes
100
Who thought of seafloor spreading?
Harry Hess
100
What method was used to map the seafloor?
Sonar
100
True or False:

Earth's magnetic field always had the same orientation .

False; Earth's magnetic field  has not always had the same orientation.
100
What are the mid-ocean ridges?
The mid-ocean ridges are mountain ranges in the middle of the seafloor.
100
What is used to measure Earths magnetic field?
The magnetometers
200
How much does the seafloor move per year?
The seafloor moves centimeters per year.
200
How was Sonar used?
Sonar is used by sound waves that are sent my a ship/boat that sends sound waves and a scientists measures the length of time it takes to bounce of the seafloor  and back up to surface.
200
How did the scientists produce an magnetic time scale?
The scientists learned the age of each these reversals, and created a calendar for these magnetic polarity reversals.
200
What made the scientists want to learn more about the mid-ocean ridges?
Maps of the mid-ocean ridges.
200
What do the magnetometers do?
As they move over the ocean, they measure the strength of the magnetic field
300
How does seafloor spreading help to explain continental drift hypothesis?
New seafloor is moving away from mid-ocean ridges as new oceanic crust is formed.Adding more seafloor, the ocean becomes wider and eventually moves the continents apart.
300
What was another technology that was used to determine the age of the seafloor?
Seafloor Drilling
300
What rocks recorded the magnetic polarity reversals?
Igneous Rocks
300
What did the scientists learn about the mid-ocean ridges compared to the Earth?
More heat is escaping from Earth at the mid-ocean ridges than at other locations in the oceans.
300
True or False:

Scientists use magnetometers to collect data about Earth's magnetic field.

True
400
What is seafloor spreading?
Seafloor spreading is the process by which new seafloor is continuously made at the mid-ocean ridges.
400
How is seafloor drilling used? And why?
Seafloor drilling is used by a boat that could drill and collect samples of rocks. It is used to collect rocks and if they are older, it determines that they are farther away from mid-ocean ridges. And if younger, closer to mid-ocean ridges.
400
How did rocks record the magnetic reversals?
This happens along the mid-ocean ridge as oceanic crust forms from lava and cools. Tiny crystals record the magnetic field orientation that existed when the crust cooled.
400
True or False;

The flow of heat from the crust increases the closer you get to a mid-ocean ridge.

False;The flow of heat from the mantle increases the closer you get to a mid-ocean ridge.
400
How can Magnetometers travel on Earths surface?
They travel by ship, plane, and satellites.
500
Explain how convection work to create new seafloor.
Convection brings hot material in the mantle toward the surface, causing magma to form. The magma flows out as lava through the cracks along the ridge. When it cools, it becomes new seafloor.
500
How can scientists use the data to calculate the depth of water?
The scientists know the speed of sound waves water, they can calculate the data to find the depth of water.
500
What is a reversed magnetic polarity?
A reversed polarity is when normally the compass points north, but one day it points south instead of north.
500
What 2 things occur near the mid-ocean ridges?
Earthquakes and Volcanoes
500
What type of pattern does the oceanic crust make?
The oceanic crust makes a stripped when graphed because it contains alternating strips of rock with normal  and reversed polarity.