Scivra
Pro 🔒~14 min

Plate Tectonics

Continental drift, earthquakes, volcanoes, and mountain building

How it works

Earth's outer shell (lithosphere) is divided into about 15 major tectonic plates that float on the semi-molten asthenosphere. These plates move 2-10 cm per year driven by convection currents in the mantle. Convergent boundaries (plates collide): continental-continental creates mountain ranges (Himalayas); oceanic-continental creates subduction zones, ocean trenches, and volcanoes; oceanic-oceanic creates island arcs. Divergent boundaries (plates separate): creates rift valleys (East Africa) on land, mid-ocean ridges under the sea (seafloor spreading). Transform boundaries (plates slide past each other): creates strike-slip faults and earthquakes (San Andreas Fault). About 250 million years ago, all continents were joined in one supercontinent called Pangaea, which has since broken apart.

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Step-by-step

  1. Choose a boundary type and watch the animation.
  2. Convergent: watch mountains build or crust subduct into the mantle.
  3. Divergent: watch the gap widen and magma fill it.
  4. Transform: watch earthquakes occur along the fault line.
  5. Use the Timescale slider (Pro) to watch millions of years of plate movement in seconds.
  6. Enable Pangaea to watch continental drift.

Key formulas

  • Speed≈2−10 cm/yr≈1−5 in/yr\text{Speed} \approx 2-10\,\text{cm/yr} \approx 1-5\,\text{in/yr}Tectonic plates move at about the speed your fingernails grow
  • Convergent→mountains/trenchDivergent→rift/ridge\text{Convergent} \to \text{mountains/trench} \quad \text{Divergent} \to \text{rift/ridge}Boundary type determines geological features

Frequently asked questions

Why do volcanoes and earthquakes cluster along specific zones on Earth?
They cluster along tectonic plate boundaries — where plates collide, separate, or slide past each other. The Pacific 'Ring of Fire' is the boundary of the Pacific Plate, responsible for ~90% of earthquakes and many volcanoes.
How do we know that all the continents were once joined together?
Multiple lines of evidence: 1) Puzzle-piece fit of coastlines (especially Africa and South America). 2) Same fossil species found on now-separated continents. 3) Matching geological formations across ocean gaps. 4) Magnetic striping on the ocean floor showing seafloor spreading.
Why does oceanic crust subduct under continental crust at convergent boundaries?
Oceanic crust is denser than continental crust (basalt ~3.0 g/cm³ vs. granite ~2.7 g/cm³). At convergent boundaries, the denser oceanic plate sinks below the lighter continental plate (subduction). As it sinks, it melts and can form volcanoes above.
If the Atlantic Ocean grows ~2.5 cm per year, how wide will it be in 10 million years?
Width increase = 2.5 cm/yr × 10,000,000 yr = 25,000,000 cm = 250 km wider. The Atlantic is currently ~7,000 km wide, so it would be ~7,250 km in 10 million years.