Happy Earth Day!
Earth is the third planet from the sun and the fifth largest in the solar system. The earth is a big mystery. It is the only planet that has oxygen, gravity, and constant movement. The Earth consists of four concentric layers: inner core, outer core, mantle and crust. The crust is made up of tectonic plates, which are in constant motion. Earthquakes and volcanoes are most likely to occur at plate boundaries. The crust is the land and ocean where we live.
One of the best places to observe the volcanic activities is Yellowstone National Park.