There’s a reason we tend to feel sleepy around the same time each night — and why, if we don’t set an alarm, we tend to wake up at the same time in the mornings. As long as we’re not pulling ...

Volcanoes can look like small mountains or hills. A volcano is an opening in the Earth's crust that allows magma, hot ash and gases to escape. Composite volcanoes are the most common type of volcano.