Big fissure is a geological term used to describe a large crack or gap in the Earth's surface. It is also known as a CHASM, which is a five-letter word. Big fissures are typically formed by tectonic activity, such as earthquakes, and can be found in areas of high seismic activity. They can also be caused by erosion, such as water or wind. Big fissures can be very deep and wide, and can sometimes form canyons or ravines.