How is the sun involved in breaking down rocks?

Answer 1

Weathering of rocks is caused by chemical and mechanical means. Slightly acidic rainwater can react with rock surfaces, dissolving them over time. Rocks can also be affected by organic sources of chemical reactants. Heat from the sun can cause differences in temperature between the surface and the interior of a rock which can cause a loosening of the surface called exfoliation. Liquid water penetrates cracks in the rocks surface where it can freeze and expand, opening up the cracks for further attack in tandem with acidic rainwater. Plant root growth can also cause cracks to further expand, making them more vulnerable to frost expansion and chemical attack. Underlying rock which is exposed due to erosion of the overlying rock becomes free of the pressure it was previously exposed to, causing the rock to expand and break apart. Other means of weathering include the expansion of crystallizing salts that have been taken in by a rock surface, expansion due to the absorption of water, and hydraulic action from crashing waves on seashore rock formations.

Answer 2

Heat: non-uniform thermal expansion.

If you heat a rock in one area, thermal expansion causes the volume to expand locally. Since the adjacent rock is not heated, the expanding volume of rock has nowhere to go (no room to expand.) Pressure builds, and the rock eventually fractures

Answer 3

Almost all rocks are made of more than one mineral. When the Sun heats the different minerals, they expand at different rates. The uneven expansion can cause cracks and breaks.