Almost all the Earth's new crust forms at divergent boundaries, but most are
not known because they lie deep under the oceans. These are zones where two plates move away from each other, allowing magma
from the mantle to rise up and make a new crust. Divergent boundaries are where the plates move apart. Seafloor
spreading is a procces in which the magma creates new land under water and this process takes over millions of years to form
a ten foot hill cause the growth ranges from two-ten centimeters per year. The magma is buoyant and creates more ridges
and an example of this is Mid-Atlantic Ridge.
convergent is collision of two plates. A collision of a less dense continental plate with a more
denser oceanic plate collides with a continental plate and the ocean plate goes under the continental plate. This takes a
great deal of energy and results in the melting the continental crust, vulcanism occurs. The kinds of volcanoes which
can occur depends on the chemical composition of the magma which desides its viscosity and there are three different types
of flow one is Basaltic is wheni t makes lava plains or sheild valcanos, Andesite is when it makes strato-volcanoes
, Dacite or rhyolite is when it makes a crater such as St. Helens.