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.
Why your body jerks before you fall asleep. If you have ever wondered why peopleâs arms and legs twitch suddenly as they are drifting off to sleep, our resident psychologist Tom Stafford has the answer. As we give up our bodies to sleep, sudden twitches escape our brains, causing our arms and legs to jerk. Some people are startled by them, others are embarrassed. Me, I am fascinated by these twitches, known as hypnic jerks. Nobody knows for sure what causes them, but to me they represent the side effects of a hidden battle for control in the brain that happens each night on the cusp between wakefulness and dreams. Normally we are paralysed while we sleep.