What cause earthquakes?

Sure, here is a step-by-step explanation:

1. Tectonic Plate Movements: The Earth's crust is divided into several large and small pieces called tectonic plates. These plates are constantly moving, albeit very slowly, due to the convection currents in the semi-fluid asthenosphere beneath them.

2. Stress Accumulation: As these plates move, they interact with each other at their boundaries. These interactions can be in the form of colliding (convergent boundaries), moving apart (divergent boundaries), or sliding past each other (transform boundaries). These movements cause stress to accumulate in the rocks at the edges of the plates.

3. Elastic Deformation: The rocks at the plate boundaries deform elastically as they accumulate stress. This means they bend and store potential energy, much like a compressed spring.

4. Rupture and Release of Energy: When the stress exceeds the strength of the rocks, they rupture and release the stored energy. This release of energy causes the rocks to snap back to their original shape, a process known as elastic rebound.

5. Seismic Waves: The sudden release of energy generates seismic waves that travel through the Earth. These waves are what we feel as an earthquake. The point within the Earth where the rupture starts is called the focus or hypocenter, and the point directly above it on the surface is called the epicenter.

6. Aftershocks: After the main earthquake, the crust may continue to adjust to the new stress distribution, causing smaller tremors known as aftershocks.

In summary, earthquakes are primarily caused by the movement of tectonic plates and the subsequent release of accumulated stress in the Earth's crust.