If it’s south of China and east of India, it may well be Southeast Asia. Beneath the surface of this region are two fault lines. (A fault line is a break in plates under the Earth’s surface.)
Because of the fault lines, earthquakes are more common here than in many other parts of the world. So are volcanoes. The area along the edges of the Pacific Ocean is known as the Ring of Fire.
Overall, this slice of Asia has two parts. One part is mainland Southeast Asia. The other part is maritime, or island, Southeast Asia. The mainland is known for its long rivers and broad lowlands. These are separated by wooded hills and mountains. The islands are different. Some are tiny dots in the ocean. Others are very large. These often have jungle-like interiors. You might say that geography both unites and divides Southeast Asia.