"Plate boundaries are zones where crust is both created and destroyed" - Leaving Cert Geography - Question 1 - 2007

An example of a destructive boundary is the boundary between the Nazca Plate and the South American Plate, where the oceanic Nazca Plate is being subducted beneath the continental South American Plate.

At constructive plate boundaries, the process begins when tectonic plates move away from each other. As they separate, magma from the mantle can rise through the gap. This magma erupts and solidifies to form new crust. For instance, at the Mid-Atlantic Ridge, this process not only adds material to the ocean floor but also leads to the formation of new land. This continuous creation of crust contributes to the geologic activity in the region, including volcanic eruptions and the formation of new islands.

Destructive boundaries are characterized by the subduction of one plate beneath another. This process leads to the destruction of crust, particularly at oceanic-continental convergences. As the denser oceanic plate sinks into the mantle, it melts due to increasing pressure and temperature. This destruction can result in volcanic activity and the recycling of crustal material back into the mantle. The Andes mountain range is an excellent example, illustrating how the collision and subduction of the Nazca Plate beneath the South American Plate leads to both volcanic activity and geological uplift.