The discovery of sea floor spreading helps explain how the continents drift.
Plate tectonics is a branch of geology built upon theories of how continent-sized pieces of the Earth's crust move along the surface of the Earth's mantle, the layers of the planet lying beneath the Earth's surface and above its molten core. The concept of plate tectonics was affirmed in the 1950s and '60s through detailed magnetic readings of the ocean floor. These revealed two important pieces of information: that the Earth's magnetic field changes polarity and that new crust is being formed on the ocean floor through volcanic activity. This latter phenomenon, known as "sea floor spreading," starts as a rift in the continental land mass. Plates move apart and form cracks that are filled with liquid volcanic rock, or magma, which seeps out onto the ocean floor, extending it. You can construct a simple model that visually shows the change in polarity to postulate sea floor spreading.
Instructions
1. Using a rolling pin roll out both colors of clay so they are approximately 3 millimeters thick.
2. Use the knife and ruler to cut strips of clay approximately 1 centimeter by 10 centimeters.
3. The strips of clay should alternate. The "valley" should be in the center and should follow the length of an individual strip.
Place the strips on the tray, alternating between both colors.
4. Create a small valley in the clay length-wise across the entire tray. This represents the rift valley formed when new layers of sea crust are pushed out of the earth. The alternating colors of clay represent the different magnetic fields that ocean rocks acquire from changes in polarity over time.
Tags: floor spreading, ocean floor, both colors, changes polarity, colors clay, strips clay
