What is a downward fold of a rock called?

Volcanic irruption is most likely to be violent when a) volcanoes near to the sea b) the neck of the volcano is sealed by a plug c) the lava is viscous d) the lava reaches the surface through a fissure e) the volcano is on the ocean floor

What type of coastline is commonly found along the western side of the america’s

What is the main source of phosphorus?