The Theory of Plate Tectonics Science 10 Evidence

The Theory of Plate Tectonics Science 10

Evidence for Plate Tectonic Theory 1. Volcano & Earthquake Locations 2. Sea Floor Spreading & Rocks on the Ocean floor 3. Paleomagnetism 4. Direct Measurement

1. Volcano and Earthquake Locations: Do you notice anything about the location of earthquakes and volcanoes? àThey occur at plate boundaries!

2. Sea Floor Spreading • Convection causes the hot magma to rise and it forces its way through the crust at mid-ocean ridges. • As the magma pushes through the crust it forms new sea floor and pushes the older rock aside in both directions.

• Younger rocks are found close to the Mid. Atlantic Ridge.

4. Paleomagnetism • Earth is like a giant magnet with its own magnetic field. • This magnetic field has not always been the same. Over thousands of years, it can actually switch—the north magnetic pole becomes a south pole and vice versa. This is called Magnetic Reversal.

4. Paleomagnetism continued… • When rocks form in the presence of this magnetic field the iron and other metals in the rocks actually align with this field! This is Magnetite, a mineral that contains iron.

4. Paleomagnetism continued… • When oceanographers used a magnetometer to measure magnetism on the sea floor, they noticed “stripes” of rock with the same magnetic polarity on both sides of the mid. Atlantic Ridge. . What do you think this means?

5. Direct Measurement • We can actually measure the rate of sea floor movement! You can go see for yourself in Iceland where the Mid-Atlantic Ridge comes onto the land.

Iceland Rift