Divergent and convergent boundaries and what they form.
A divergent boundary is formed when two plates diverge or move apart from each other. This happens as magma spreads beneath the Earth’s surface. Since new landforms are created along such a plate boundary, it is also called a constructive boundary.
Oceanic-Oceanic plate divergence
This process is called sea floor spreading. Magma rises to fill the gap created at the plate boundary. Magma solidified to create new sea floors. Hence, younger rock found nearer the boundary. As Oceanic crust moves apart, fractures appear at the boundary. Magma from beneath the Earth’s crust rise to fill the gap created. As magma cools and solidfies, a ridge is formed on the sea floor. This is called a Mid Oceanic Ridge.
Continental-Continental plate divergence
As continental crust move apart, they are stretched, causing fractures to form at the boundary.
The land in between the two continental crusts sinks as a result of the divergent movement.
The linear depression formed is called a rift valley.
Over time, gap left behind may also be fille to form a water body. Sea bed pushes the landmasses apart and the sea grows wider.
A convergent boundary is formed when two plates move towards or collide into each other. The denser or heavier crust is forced under the less dense or lighter crust, into the mantle. This process is called subduction and it takes places at the subduction zone. As the sinking crust moves down into the mantle, the great heat melts the crust. Hence, it is also called a destructive boundary.
Oceanic-Continental plate convergence
When an oceanic crust collides into a continental crust, the denser oceanic crust is forced to sink under the less dense continental crust, forming an oceanic trench. The oceanic crust is denser because minerals that make it up have higher densities. Sinking crust melts to become magma which then rises to the Earth’s surface through fractures to form volcanoes. The compression of the continental crust also forms a range of fold mountains.
Oceanic-Oceanic plate convergence
When two oceanic crusts collide, denser oceanic crust will be forced under less dense oceanic crust. The older the sea floor, the denser it will be. Sinking crust will melt to become magma. Some of the magma rises through fractures in oceanic crust, forming undersea volcanoes. This volcanoes build up and appear above the sea to form volcanic islands.
Continental-Continental plate convergence
Massive bending and folding of crust when two crusts push against each other forms a range of fold mountains.