All three are definitely part of skateboarding.
The wheels for example, are usually made of polyurethane. The trucks are usually an aluminum alloy. There are other metals and plastics used as well. These are all made using chemistry.
Biology is also a big part of it. People fall off of their skateboards all of the time and injure themselves. They get scrapes, bruises, cuts, and even broken bones. In addition, the way people use their bodies to maneuver the skateboard is an example. It takes balance and coordination to properly control a skateboard. There are many muscles involved.
Earth science is involved as well. People ride skateboards over different types of terrain. The terrain may be flat, hilly, etc.
You can relate chemistry to skateboarding because boards and wheels, especially, are made using chemistry. There is a lot of chemistry that goes into making the strongest wheels and such possible.
Biology can come into it as your muscles get stronger when used for skateboarding. If you fall down and scrape yourself and the wound gets infected, that's biology.
The cement that you skate on is made from various kinds of things that come from the earth. In addition, if you skate down a hill, that hill is there because of geology.