Plate Tectonics worksheet covering continental drift and seafloor spreading concepts.

Let’s go through each section step by step and fill in the blanks with the correct science terms.

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Section 1: Continental Drift

1. The continental drift hypothesis—continents have moved slowly to their current location.
→ This is just a statement, no blank here.

2. All continents were once connected as one large landmass now called Pangaea.
→ “Pangaea” is the name of the supercontinent that existed long ago.

3. Evidence for continental drift:
a. The land mass broke apart, and the continents drifted to their present positions.
→ Makes sense — continents moved after Pangaea split.

b. Similar fossils fit of the continents.
→ Scientists found matching fossils on different continents, like puzzle pieces fitting together.

c. Remains of warm-weather plants in cold areas and glacial deposits in warm areas suggest that continents have moved.
→ If you find tropical plant fossils in Antarctica or ice age rocks in Africa, it means those places used to be in different climates — so they must have moved!

d. Similar rock structures are found on different continents.
→ Mountain ranges and rock layers match across oceans — another clue continents were once joined.

e. At first, continental drift was not accepted because no one could explain how or what force continents had moved.
→ People didn’t believe it until they figured out plate tectonics — what actually pushes the continents.

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Section 2: Seafloor Spreading

A. Using the mid-ocean ridges in many oceans, scientists discovered a system of underwater mountain ranges called the mid-ocean ridge system.
→ It’s a giant chain of mountains under the ocean where new seafloor is made.

B. In the 1960s, Harry Hess suggested the theory of seafloor spreading to explain the ridges.
→ He said new crust forms at ridges and spreads outward.

1. Hot, less dense material below Earth’s crust rises upward to the surface at the mid-ocean ridges.
→ Magma from the mantle comes up through cracks in the crust.

2. Then, it hardens sideways, carrying the seafloor away from the ridge.
→ As magma cools, it becomes new ocean floor and pushes older rock aside.

3. As the seafloor spreads apart, magma moves up and flows from the cracks, cools, and forms new seafloor.
→ Magma fills the gap and solidifies into new rock.

C. Evidence for seafloor spreading:
1. Younger rocks are located at mid-ocean ridges.
→ New rock forms right at the ridge, so it’s youngest there.

2. Reversals of Earth’s magnetic field are recorded by rocks in strips parallel to ridges.
→ When lava cools, iron minerals line up with Earth’s magnetic field. Sometimes the field flips — and we see those flip patterns in stripes on the seafloor!

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Final Answer:

Section 1:
2. Pangaea
3a. continents
3b. fossils
3c. cold; warm
3d. rock
3e. how; what force (or “mechanism”)

Section 2:
A. mid-ocean ridge system
B. seafloor spreading
B1. crust
B2. seafloor
B3. magma
C1. Younger
C2. magnetic field