Sedimentary rocks: Limestone cliffs in Saudi Arabia Before sedimentary rocks When the Earth was first forming, about six billion years ago, there weren't any sedimentary or metamorphic rocks. The only [...]
Erosion of a cliff in Canada Igneous rocks came first When the Earth first formed, about four and a half billion years ago, it was all liquid rock and liquid [...]
What is metamorphic rock? Slate rocks in Cascadilla Gorge, Ithaca, New York Metamorphic rocks form under pressure About 450 million years ago, some of the sedimentary rocks began to transform [...]
