What is the name of a measure of a waves crest's height to its baseline?

Which of the following best describes the economy of africa?

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

Based on the information in the graph, what can you conclude about humans in the world in general?