Chemical Weathering. Chemical weathering takes place in almost all types of rocks. Smaller rocks are more susceptible, however, because they have a greater amount of surface area. Chemical reactions break down the bonds holding the rocks together, causing them to fall apart, forming smaller and smaller pieces.
Autos generally are ready to harvest sooner than photoperiod. Most autos are ready to harvest 65-90 days after being sprouted from seed. Some super autos have been bred to grow very big and can take up to 100 days before harvest.
Carrots are planted as seeds, and can take up to three weeks to germinate. If you're growing the common elongated orange variety, figure a good 12 weeks before the carrots are ready to harvest. The shorter, stubbier varieties may be reaped even earlier. It's best to read the back of the seed packet.