HOW A TRENCH IS MADE
The movie maker James Cameron in made a dive in Mariana Trench which stretched about 7 miles deep and scientists only know what are below the ocean trench. Ocean trenches are formed by a specif plate boundary and it is called a subduction zone this happens when one oceanic plate crashes into another oceanic plate. The oceanic plates are made up a type of denser rock which is called basalt, when a dense oceanic plate meets or collides with the other it sinks back into the mantle which creates a trench in the ocean floor leaving a trench.
HOW VOLCANO'S ARE FORMED
A volcano is an opening in the ground that spits hot rocks and magma but after magma hits the earths surfac it turns into lava because it has cooled down. Volcanoes are formed when two plates hit each other and one goes under the other. Because one sinks back into the mantle and the lava that is being pushed up makes it to the crater of the volcano threw a series of cracks. In the world there are about 1,500 volcano's out of those only about 52 that are active.