Constructive Plate Boundary
Constructive Plate Boundary
Definition: (Divergent boundary) - Where two plates move away from each other and new oceanic crust is formed.
What is a Constructive Plate Boundary? At divergent plate margins, plates are moving apart and new lithosphere is being created.
In the oceans, this has produced the mid ocean ridge system, which can also be described as a global range of underwater mountains. Well known ocean ridges include the Mid Atlantic Ridge, the East Pacific Rise, the Juan de Fuca Ridge, and the Galapagos Rise.
Within continents, divergent margins produce rift valleys such as the Red Sea and East African Rifts; and the lesser known West Antarctic Rift.
Mid-Atlantic Ridge: The North American and Eurasian Plates are moving away from each other along the line of the Mid Atlantic Ridge. The Ridge extends into the South Atlantic Ocean between the South American and African Plates. The ocean ridge rises to between 2 to 3 km above the ocean floor, and has a rift valley at its crest marking the location at which the two plates are moving apart.
The Mid Atlantic Ridge, like other ocean ridge systems, has developed as a consequence of the divergent motion between the Eurasian and North American, and African and South American Plates. As the mantle rises towards the surface below the ridge the pressure is lowered (decompression) and the hot rock starts to partially melt. This produces basaltic volcanoes when an eruption occurs above the surface (Eyjafjallajökull in Iceland) and characteristic basalt “pillow lava” in underwater eruptions. In this way, as the plates move further apart new ocean lithosphere is formed at the ridge and the ocean basin gets wider. This process is known as “sea floor spreading” and results in a symmetrical alignment of the rocks of the ocean floor which get older with distance from the ridge crest.
Evidence for this process comes from the magnetic properties of the erupted basalt. The Earth’s magnetic field has been shown to
Definition: (Divergent boundary) - Where two plates move away from each other and new oceanic crust is formed.
What is a Constructive Plate Boundary? At divergent plate margins, plates are moving apart and new lithosphere is being created.
In the oceans, this has produced the mid ocean ridge system, which can also be described as a global range of underwater mountains. Well known ocean ridges include the Mid Atlantic Ridge, the East Pacific Rise, the Juan de Fuca Ridge, and the Galapagos Rise.
Within continents, divergent margins produce rift valleys such as the Red Sea and East African Rifts; and the lesser known West Antarctic Rift.
Mid-Atlantic Ridge: The North American and Eurasian Plates are moving away from each other along the line of the Mid Atlantic Ridge. The Ridge extends into the South Atlantic Ocean between the South American and African Plates. The ocean ridge rises to between 2 to 3 km above the ocean floor, and has a rift valley at its crest marking the location at which the two plates are moving apart.
The Mid Atlantic Ridge, like other ocean ridge systems, has developed as a consequence of the divergent motion between the Eurasian and North American, and African and South American Plates. As the mantle rises towards the surface below the ridge the pressure is lowered (decompression) and the hot rock starts to partially melt. This produces basaltic volcanoes when an eruption occurs above the surface (Eyjafjallajökull in Iceland) and characteristic basalt “pillow lava” in underwater eruptions. In this way, as the plates move further apart new ocean lithosphere is formed at the ridge and the ocean basin gets wider. This process is known as “sea floor spreading” and results in a symmetrical alignment of the rocks of the ocean floor which get older with distance from the ridge crest.
Evidence for this process comes from the magnetic properties of the erupted basalt. The Earth’s magnetic field has been shown to