Sandstone: Rock for Crack Climbing. Sandstone is a sedimentary rock, a rock type that encompasses a wide variety of characteristics and is deposited directly on the earthâs surface. Roughly 75% of the earthâs land surface is covered with some type of sedimentary rock. Sedimentary rocks like sandstone form when minute rock particles, often from granite, are deposited by wind and water on earth surfaces.
8. 1  Other Causes. 2  Diabetes causes arms or hands and feet to fall asleep even when one is awake and relaxed. 3  Hand surgery and arthritis damage or irritate the nerves.
Doctors and scientists aren't really sure why they happen, but they have a few theories. One theory is that your brain misunderstands the sensation of your muscles relaxing as you drift off to sleep. It's normal for the muscles to relax, but the brain gets confused, and, for a minute, thinks you're falling. In response, the brain causes your muscles to tense up so you catch yourself before you fall down.