Across
1
Substance with pH below 7
4
Unit of energy
5
Naturally occurring inorganic solid
6
Absolute temperature scale unit
9
Preserved remains of ancient life
11
Form of thermal energy
12
Path of a planet around the sun
Down
2
Precious yellow metallic element
3
Tectonic landmass section
5
Molten rock beneath Earth surface
7
Element found in all living things
8
Nerve cell in the brain
10
Blocking of light by a celestial body
13
Basic unit of life