Flood basalt

Flood basalt is when very hot, melted rock (called magma) erupts out of a volcano, and then spreads like a flood over the ground. This molten rock is usually black or dark green in color, and when it hardens it makes a thick layer of rock called basalt. Flood basalts can be very large and cover thousands of square miles. They can also be very deep and pile up to depths of hundreds of feet. Flood basalts are very impressive to see!