Intrusive igneous rocks form from the slow cooling of magma within Earth's crust, which generally creates larger crystals and a coarse-grained texture.
The most important zone in the vertical distribution of the water is the surface zone and is asp called as the photic zone and is found to a few 200 m from the surface.
Also characterized by the small surface zone ad blow which is the deep and dark zone and aphotic zone includes the inter-tidal, the nitric , and the oceanic zones. It has a depth of 4000 meters.
In between they lies the transition zone and is about 1000 metes and organisms that live in this zone are bio-luminescent.