Scientists have detected more than 160 asteroid impact craters on Earth's surface as of July 2014. Most of these were cataloged before 1950, and a few new ones are discovered each year. The largest impact crater is 236 miles across in South Africa due to an impact that happened more than 2 billion years ago. Asteroids more than 6 miles across create layers of pulverized rock on the surface.Know More
Impact craters on Earth come in two different types. Smaller craters are less than 2 miles in diameter with a bowl-shaped depression and some rock fill in the middle. Larger craters are more than 2 miles across with a central peak, melted rocks and a slumped rim.
The Vredefort Crater in South Africa is a UNESCO World Heritage Site. The impact crater is the largest and one of the oldest on Earth. The Sudbury Basin in Ontario, Canada, is 1.8 billion years old and 81 miles in diameter. This part of Canada is the second-largest impact crater in the world.
Large asteroids more than 6 miles wide that strike the Earth create plumes of pulverized rock, called spherules, that are ejected into outer space due to the violence of the impact. Spherule layers settle back to the surface, and these layers are detected by scientists. Spherule layers are dated by surrounding layers of rock to give geologists an idea of when large asteroid impacts occurred.Learn more about Geology
Magma rises to the Earth's surface due to a combination of differences in density with other rocks in the crust and pressure. The differences in density cause it to move upward until its density is the same as the other rocks in the crust. It then builds pressure, causing it to rise to the surface.Full Answer >
Basalt is primarily formed by the extrusion of lava flows onto the surface of the earth during a volcanic eruption. The intrusion of a narrow sill or igneous dike below the crust also results in the formation of basalt.Full Answer >
Mineral crystals form at the surface and deep within the Earth. They grow from vapors that contain plenty of mineral components. Many crystals form in volcanic locations where hot gases encounter cool temperatures.Full Answer >
The average depth of Lake Huron is approximately 195 feet, but its deepest point reaches 750 feet below the surface. This massive body of water is located between Michigan and Canada, stretching 206 miles long and 183 miles wide.Full Answer >