The Gambia has no migrating wildebeest, giraffes or any of the large animals commonly associated with Africa. However without leaving your hotel you can see a breathtaking variety of bird life, in addition to monkeys and lizards. Baboons and crocodiles can be seen nearby and then far up the river, hippos.
As the gasses collect in the magma chamber, the pressure rises. It is possible for the pressure to rise so much that the chamber cannot contain the magma and it erupts explosively. Some US Parks that have active volcanoes formed as the result of subduction related processes are: 1  Crater Lake National Park, OR.
Volcanoes occur at divergent plate boundaries because of the new crust formed by solidifying of magma on the ocean bed which is very weak so the heat and pressure from the magma chamber will become too high to handle and there will be an eruption. Volcanoes form where the earth's crust is thin an the magma can flow to the surface easier.