Why do earthworms come out of the soil after heavy rain?

Because earthworms live in cracks in the soil and have no special respiratory organs, they breathe through the skin. Its skin surface is often so moist that oxygen dissolves in the mucus on the skin surface and penetrates into the capillaries under the skin. Carbon dioxide in capillaries can also penetrate from the skin. Earthworms live well in the soil when the gaps in the soil are filled with air. But after the heavy rain, the cracks in the soil were full of rain, and oxygen was scarce. Earthworms found it difficult to breathe, so they got out of the soil.