There are mountain ranges in the middle of the ocean floor. because of the higher elevation gravity pushes down on the edges of the plates. this is called

ridge push

slab pull

There are mountain ranges in the middle of the ocean floor. Because of the higher elevation gravity pushes down on the edges of the plates. This is called ridge push.

Ridge push is a simple explanation of the height of the landforms based on the gravity and the elasticity of the underlying rock. It says when a landform gets too much higher, the weight of the overlying rock and soil pushes the landform back to plains. Thereby an equilibrium is maintained.  

Slab pull is a theory proposed which visualizes the earth interior as a pool of hot molten lava that has a convection current going on. It explains why the crust of the earth continuously moves slowly and forms mountains and other rift valleys.  

sorry, but you do not have posted the diagram.

the oldest known insects are believed to live around 400 millions ago as suggested by the fossil records.   some plants having woody stems also evolved during this time.

after the evolution of insects the first four legged species or the tetrapods evolved in shallow freshwater habitats from the intermediate species approximately 397 million years ago. the tetrapods went on conquering the land giving rise to amphibians, reptiles, mammals and birds.

the major split in tetrapods first occurred 340 million years ago branching off from amphibians.

363 million years ago when the carboniferous period began the insects started roaming on land and taking flights, following which the four limbed tetrapods adapted in the terrestrial habitat.