Answer: The Precambrian Era comprises all of geologic time prior to 600 million years ago.
Explanation: The Precambrian was originally defined as the era that existed before the emergence of life in the Cambrian Period. It is known that life on Earth began by the early Archean and that fossilized organisms became more and more abundant throughout Precambrian time.
Answer: He found a rock, and the crystals inside are minerals.
Options:
- He found a rock, and the crystals inside are minerals.
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He found a mineral, and the crystals inside are rocks.
- He found a rock, and the crystals inside are rocks, too.
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He found a mineral, and the crystals inside are made of dirt.
Explanation:
A rock differs from a mineral. While they are both solid, a mineral has a crystalline structure while a rock does not have a specific structure. Rocks are made up of different mineral structures and that is what Joseph discovered on dropping the rock, one of the component minerals in the rock. For example, a type of rock, slate may consist of feldspar, quartz among many other minerals.
Answer:
The heat equation can be written as. ∂ u ∂ t = α ∇ 2 u. where u(x, y, t) is the temperature field that varies in space and time, and α is the thermal diffusivity constant.
