Plate tectonics

Who first suggested continental drift, and why was it rejected?

Alfred Wegener (1911), because of current paradigm and he added incorrect, unnecessary answers toquestions he didnt know

What evidence is there for continental drift?

• Coastline similarities

• glaciation in now tropical places

• remains of tropical plants in antarctica

• fossil remains of plants and animals that lived in restricted areas across many different continents

What is paleomagnetism?

as magma cools, the iron the in minerals aligns along the magnetic field (N-S)

The alignment varies with latitude (as magnetic north does), which allows geologists to see how far removed the rock is from the area that it formed (due to continental drift)

What is a polar wandering curve?

Magnetized rocks from different times in the same area show a shift in pole direction- this wave makes it appear that the poles moved, but we know its that the continents drifted over time

what is reversely magnetized rock

Earths poles switch directions every now and again (geologically) so when rocks form during a pole reversal, they are said to be reversely magnetized

Why are there magnetic patterns on the seafloor?

Seafloor spreads through midocean ridges- magma fills the crack that are left as the crust splits, and crystalizes, magnetizing the mineral in whatever direction the poles are currently at (which changes back and forth overtime)

How quickly does the seafloor spread?

0.5-20 cm per year (3sqkm of new floor generated across the world in a year)

What is the lithosphere?

The upper mantle and crust (solid and brittle), which hold the continents

What is the asthenosphere?

The lower mantle that is plastic and moving (plates of the lithosphere ride on top)

WHy are mid ocean ridges critical for ocean health?

Seawater interacts with the new basalt as it forms and carries metals and chemicals back into the water (forms black smokers, chemical vents where life formed)

Which plate is forced under in subduction at convergent boundaries?

Always the oceanic plate- similar in density to underlying asthenosphere, so forced under by heavier continental plate

Whats an example of a transform fault?

the san andreas fault

What are mantle plumes?

Jets of hot material arising from deep in the mantle that remain stationary while plates move over them - leaves a trail of old volcanoes which show the movement of the plate