Geopix UK - Tectonics

Continents and Oceans

If we are setting out to explore the way in which the Earth's surface has developed and how it has evolved into its present-day pattern, a good place to start is with a straightforward description the continents and oceans.

Inevitably, some questions will arise. The search for the answers will help us to understand the Earth's Tectonics.

Ocean basins cover two-thirds of the Earth's surface;
The deepest part of the Oceans is not in the middle;
The deepest part of the oceans is often at the edge;
The continents are granitic, the oceans are basaltic;
The oldest oceanic crust is only 200 million years old;
The oldest continental crust is over 4000 million years old;

why isn't the spin of the Earth out of balance?
why is there a mountain chain along the middle?
how are these deep trenches formed?
why are the compositions so different?
where has the older oceanic crust gone to?
why isn't there any oceanic crust of that age?

Here are some more observations about the continents and oceans.
Each statement gives rise to further questions - any suggestions?

The continents are made of igneous, metamorphic and sedimentary rock.
The mid-ocean ridges are made (largely) of basalt.
The highest part of the continents is usually the edge rather than in the middle.
Major mountain ranges are 'fold' mountains resulting from intense compression.
Other structures, such as rift valleys, are caused by extension of the crust.
The ocean basins are deep 'holes' in the surface of the Earth.
The continental shelves vary in width; for example, alongside the deep ocean trenches, the continental shelf is narrow.
In 1912, Wegener suggested the idea of continental drift, that continents can move across the surface of the Earth.

The East African Rift Valley.

Geopix Study Topic "Continents and Oceans"

describes the major features such as the abyssal plain, mid-ocean ridge, fold mountains and cratons;
outlines the crustal composition and structure of the continents and oceans;
describes the junction between the continents and oceans;
introduces the importance of the geothermal gradient.

To order the "Tectonics" Study Guide on CD, or the "Continents and Oceans" Study Topic by download,
please visit the Geopix on-line store

The "Continents and Oceans" Study Topic includes the following pages: