Unit 1: Seafloor Spreading

Multiple Choice

What is seafloor spreading?

• The movement of tectonic plates towards each other at ocean trenches.
• The process of ocean water evaporating to form clouds.
• Seafloor spreading is the formation of new oceanic crust at mid-ocean ridges as tectonic plates diverge.
• The sinking of oceanic crust into the mantle at subduction zones.

Multiple Choice

Who proposed the theory of seafloor spreading and what is the main process involved?

• Harry Hess; new oceanic crust forms at mid-ocean ridges and moves outward

• Alfred Wegener; continents drift over the mantle

• Isaac Newton; gravity pulls continents together

• Marie Tharp; ocean trenches are formed by erosion

Match

Match the following

• Magnetic objects points North

• Magnetic objects that point South

• Magnetic field changes directions

Normal Polarity

Reversed Polarity

Reversed Polarity

• Normal Polarity

• Reversed Polarity

• Reversed Polarity