Tectonic Plate Movements

What Are Tectonic Plates?

Tectonic plates are massive, irregularly shaped slabs of rock that make up the Earth’s lithosphere (the outermost layer of Earth). These plates move slowly over the asthenosphere, a more fluid-like layer beneath the lithosphere.

• Lithosphere: Earth’s rigid outer shell, divided into tectonic plates.
• Asthenosphere: A semi-fluid layer on which tectonic plates “float” and move.
• There are seven major plates (like the Pacific and Eurasian plates) and several minor ones.
• Tectonic plates are constantly in motion but very slowly, moving only a few centimeters per year.

How Do Tectonic Plates Move?

Convection Currents: Heat from Earth’s core causes the mantle’s molten rock to rise and fall, pushing plates apart or pulling them together.

Types of Plate Boundaries:

• Divergent Boundaries: Plates move apart, forming new crust (e.g., the Mid-Atlantic Ridge).
• Convergent Boundaries: When plates move towards each other, they can collide. This causes the landmasses on the plates (like continents) to push together, forming mountains, or one plate can sink beneath the other, causing earthquakes and volcanoes. (e.g., the Himalayas).
• Transform Boundaries: Plates slide past each other, causing earthquakes (e.g., the San Andreas Fault).

Fun Facts

Here are some interesting facts about tectonic plates:

• The Pacific Plate is the largest tectonic plate known as the “Ring of Fire” due to its many volcanoes.
• Tectonic plates move about as fast as your fingernails grow—a few centimeters yearly!
• The Himalayan Mountains are still rising because the Indian plate is pushing into the Eurasian plate.
• The Mid-Atlantic Ridge is the longest mountain range in the world, mostly underwater!

Review

Let’s quickly recap what we learned about tectonic plates:

• What layer do tectonic plates move on? Asthenosphere
• What type of boundary forms a new crust? Divergent Boundary
• What causes tectonic plates to move? Convection Currents
• What type of boundary causes earthquakes and volcanoes? Convergent Boundary