Soil form as rock is broken down by weathering and mixes with other materials on surface. soil is constantly being formed wherever bedrock is exposed. over time soil develops layers called horizons. a soil horizon is a layer of a soil that differs in color and texture from the layers above or below it.
A possible cause was a meteorite hit the earth. it caused many organisms to become extinct because it blocked out the Sun so plants couldn't grow and herbivores couldn't eat the plants and carnivores couldn't eat herbivores.
