How do scientists know when oxygen first appeared in the Earth's atmosphere?
The mass extinction of Archaea.
The decrease of CO2 in the Earth's atmosphere.
o The formation of snowball Earth.
o The appearance of red banded sedimentary rock
which was produced when oxygen reacted with and
precipitated dissolved iron in the oceans.

Which set of characteristics best describes igneous rock? a) largest type of rock, made of organic matter, hardest type of rock b) least abundant type of rock, made of other rocks, made mostly of minerals c) found on all continents, contains wavy bands of stripes, contains fossils d) most abundant type in earth's crust, made of magma/lava, contains no fossils

How might this scientific phenomena be explained? a paper clip floats on water.

What is the energy in joules of a mole of photons associated with visible light of wavelength 486 nm?