We do not feel any motion because these speeds are constant. The rotation and orbital speeds of the Earth stay the same and so we do not feel any acceleration or deceleration. You will only feel motion if your speed changes. Have you ever been on an airplane? On my many hated rides on airplanes, when the airplane accelerates and takes off, I feel a lot of motion. However, I realise that once in the air, I feel as though the airplane is not moving at all, as if we were just hovering aimlessly in the sky.
I just decided to share this bit of information with all of you as after Miss J's lesson last week, this question just randomly popped into my head. I found it interesting and this was the result of my research!
Also, do you remember how the plates of the Earth's crusts form volcanoes? If you remember, you may have guessed that volcano eruptions are related to the Earth's second outermost layer, the mantle.
When rock inside the Earth becomes hot enough it melts. The molten rock(magma) is less dense compared to the surrounding solid rock. The relatively low density of the magma causes it to rise to the surface of the Earth. If the magma contains water and dissolved gases, when the magma reaches the surface, the water and dissolved gases will suddenly expand into steam and gas, causing a violent eruption.
The link below has pictures that will help you understand!
http://library.thinkquest.org/03oct/01550/eruptions.htm
