Earthquakes occur throughout the world, but the vast majority occur along narrow belts which are a few tens to hundreds of kilometres wide. These belts mark boundaries on the planet's surface that are very active geologically. An earthquake occurs when rocks break under the stress created by the constant movement and collision of the thin jigsaw-like tectonic plates found at the surface of the Earth.
A flood is an overflow of an expanse of water that submerges land. Flooding may result from a body of water, such as a river or lake, exceeding the total capacity of its boundary, with the result that some of the water flows or sits outside of the normal perimeter of the body.