It turns out the answers are in Earth's rocks. Even the Greeks and Romans realized that layers of sediment in rock signified old age. But it wasn't until the late 1700s -- when Scottish geologist ...

The beginnings of a strange layer of molten rock deep inside the Earth may have finally been figured out by geoscientists.

Instead, it's documented in layers and layers of rock deposited over 4.6 billion years. The stretch of geologic history is commonly referred to as "deep time," and it's a concept perhaps as ...

Over time, the layers are compressed and glued together.Metamorphic rocks are formed from other rocks, igneous or sedimentary, which are heated and compressed underground.Igneous rocks are formed ...

The next layer is the mantle. Many people think of this as lava, but it's actually rock. The rock is so hot, however, that it flows under pressure, like road tar. This creates very slow-moving ...

NASA's Perseverance rover has encountered another rock on Mars that has left scientists puzzled.

Sedimentary rocks are formed by small rock pieces which are transported by rivers and laid down in layers. Chalk is a sedimentary rock. Metamorphic rocks are formed when another rock is under heat ...

What Was Happening on Earth at This Time The Precambrian is the earliest of the geologic ages, which are marked by different layers of sedimentary rock. Laid down over millions of years ...