SOLUTION: Convection current learning activity sheet in science ... - Free Printable

Problem Overview:

The task requires us to:
1. Describe the possible causes of plate movement.
2. Enumerate the lines of evidence that support plate movement.

Solution:

#### 1. Possible Causes of Plate Movement:
Plate tectonics is the scientific theory that explains the movement of Earth's lithospheric plates. The primary cause of plate movement is convection currents in the Earth's mantle. Here’s a detailed explanation:

- Convection Currents in the Mantle:
- The Earth's mantle is composed of semi-solid rock, which can flow very slowly over long periods due to its high temperature and pressure.
- Heat from the Earth's core (primarily from radioactive decay) heats the mantle material near the core-mantle boundary.
- This heated mantle material becomes less dense and rises toward the surface (a process called upwelling).
- As it rises, it cools and spreads out horizontally at the base of the lithosphere.
- The cooled, denser material eventually sinks back down into the mantle (a process called subduction), completing the convection cycle.

- Key Processes Driven by Convection:
1. Divergent Boundaries: At mid-ocean ridges, convection currents cause the mantle material to rise and spread apart. This leads to the formation of new oceanic crust as magma rises and solidifies.
2. Convergent Boundaries: At subduction zones, denser oceanic crust sinks back into the mantle, causing the overriding plate to buckle and form mountain ranges or trenches.
3. Transform Boundaries: These occur where two plates slide past each other horizontally, often resulting in earthquakes.

#### 2. Lines of Evidence Supporting Plate Movement:
Several lines of evidence support the theory of plate tectonics and the movement of Earth's lithospheric plates:

1. Fossil Evidence:
- Identical fossil species have been found on continents that are now widely separated. For example, fossils of the ancient reptile *Mesosaurus* have been found in both South America and Africa, suggesting these continents were once joined.

2. Rock and Geologic Feature Matching:
- Similar rock types and geological structures (e.g., mountain ranges, sedimentary layers) are found on different continents, indicating they were once part of the same landmass. The best example is the Appalachian Mountains in North America and the Caledonian Mountains in Europe and Greenland.

3. Paleomagnetism:
- Rocks contain magnetic minerals that align with the Earth's magnetic field when they form. By studying the orientation of these minerals in rocks of different ages, scientists can determine how continents have moved relative to the Earth's magnetic poles over time.

4. Seafloor Spreading:
- The discovery of symmetrical patterns of magnetic stripes on either side of mid-ocean ridges provides strong evidence for seafloor spreading. These stripes result from the periodic reversals of Earth's magnetic field, which are recorded in the basaltic rocks of the ocean floor as they cool and solidify.

5. Age of Oceanic Crust:
- The oceanic crust is youngest at the mid-ocean ridges and gets progressively older as you move away from the ridge. This supports the idea that new crust is being formed at the ridges and pushed outward as the plates move.

6. Volcanic and Seismic Activity:
- Most volcanic and seismic activity occurs along plate boundaries. For example, the Ring of Fire around the Pacific Ocean is a zone of intense earthquake and volcanic activity due to subduction zones.

7. Continental Fit:
- The shapes of continents, particularly the west coast of Africa and the east coast of South America, fit together like puzzle pieces, suggesting they were once joined.

8. Glacial Deposits:
- Glacial deposits and striations found in areas like South America, Africa, India, Antarctica, and Australia provide evidence that these continents were once part of a single supercontinent (Gondwana) during a glacial period.

Final Answer:

\[
\boxed{
\text{1. Causes of Plate Movement: Convection currents in the mantle drive plate movement through processes like divergence, convergence, and transform faulting.}
}
\]
\[
\boxed{
\text{2. Lines of Evidence: Fossil evidence, rock matching, paleomagnetism, seafloor spreading, age of oceanic crust, volcanic and seismic activity, continental fit, and glacial deposits.}
}
\]