Reading: A restless planet

Earth’s surface looks still, but it is made of enormous slabs of rock called tectonic plates. These plates shift very slowly over a softer layer deep inside Earth. Their edges meet in different ways: they may move apart, press together, or slide past one another. Stress can build up where two plates are stuck against each other. When the rocks suddenly slip, stored energy travels through the ground as seismic waves. The shaking is an earthquake. Strong shaking can damage buildings, split roads, and trigger landslides on steep slopes. How much damage occurs depends partly on the earthquake’s strength and on how well nearby structures are built. Some volcanoes form near places where plates meet. In certain locations, rock beneath the surface melts into magma. Magma can rise through cracks and collect underground. If it reaches Earth’s surface, it is called lava. An eruption may send molten rock, fine volcanic particles, and gases into the surrounding area. These materials can harm people, animals, and plants nearby, although volcanic ash can also add minerals to soil over time. Scientists monitor regions where earthquakes or eruptions may occur. Instruments can record ground motion, and satellites can detect changes in a volcano’s shape. These observations help experts assess danger and share warnings. They cannot tell exactly when every earthquake or eruption will happen, so communities also prepare by practicing safety plans and making buildings more resistant to shaking.