The Earth's crust is broken up into pieces called plates. Heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core. The convection currents move the plates. Where convection currents diverge near the Earth's crust, plates move apart. Where convection currents converge, plates move towards each other. The movement of the plates, and the activity inside the Earth, is called plate tectonics.
Plate tectonics cause earthquakes and volcanoes. The point where two plates meet is called a plate boundary. Earthquakes and volcanoes are most likely to occur either on or near plate boundaries.
The map shows the world's tectonic plates and the distribution of earthquakes and volcanoes.
Dark energy is the term to refer to the force that is causing an expansion of the universe to accelerate. It is estimated that the universe is 68.3 percent <span>dark energy, 26.8 percent dark matter, and 4.9 percent ordinary matter.</span>
