since continents of the world are very old, why haven't they been eroded to sea level?

Answer 1

Contenents undergo forces that lift them.

Maruyama envisions a half-billion-year cycle of superplume activity that first draws continents together and then splits them apart. He fits the concept into the fully accepted theory of plate tectonics, which explains how the thicker, lighter continental plates float on underlying magma and bump into each other and heavier oceanic plates; clashes between plates feed volcanoes (by recycling solid crust back into the liquid magma), cause earthquakes and create mountains.

Baker drew on the earthy concept of a pot of soup on the stove to help explain how a superplume works. In a really thick soup -- a stew rather than a broth, say -- a relatively solid mass might heat up on the bottom until it suddenly broke away and traveled to the top of the mixture in one massive chunk. This would be comparable to the superplume method of transferring heat via magma from a planet's hot inner core toward a surface land mass.

By this line of thinking, which Maruyama describes in a 1994 Journal of the Geological Society of Japan paper, the ongoing collision of Indian with Southeast Asia is not only creating the Himalayan Mountains, it is the future site of a supercontinent. (Don't worry, this would be some 250 million years down the road.) Also, he hypothesizes that an underlying superplume of magma is lifting the continent of Africa. For one thing, the continent is being ripped apart at the African Rift. Also, Africa has the highest average elevation of all seven continents despite a conspicuous lack of tall mountains.

Answer 2

The haven't been eroded to sea level becasue new crust is created at mid ocean ridges.

Answer 3

they are eroded it just take forever as most of the rock it extremely durable such as granite

Answer 4

some were eroded .
But others according tectonics were resurrected

Answer 5

Tectonic plate interaction and volcanic eruptions.

Answer 6

continents are stronger than water because you can build on them

Answer 7

We're working on it, just give it time.