Your textbook has an excellent chapter on plate tectonics. Within the next few pages, I will provide some additional resources to help you understand this large, but also complicated, concept.
Let’s start our journey through plate tectonics by summarizing its key concepts:
- The Earth’s crust is broken up into plates, or sections.
- These plates are less dense than the mantle, so they float on the mantle like ice floats over water. (Ice is less dense than water.)
- Temperature differences in the mantle create convection, which causes the plates to move around.
- These plates move at very slow rates (centimeters per year) into each other, apart from each other, and rub against each other.
- While all crust is less dense than the mantle, the continents are formed of thicker crust that is relatively less dense; the oceans are made of thinner crust that is relatively denser.
- Many plates are composed of both oceanic and continental crust (such as the Atlantic coast), while some only have one type of crust.
- When these crustal plates collide, their differences in density will determine whether they subduct (like in the Western U.S.) or build huge mountain ranges (like in the Himalayas).
A hard-boiled egg is a great example of how the Earth’s crust is broken up in plates. Other planets, like Mars, are like an unbroken egg, where the shell represents the crust. The Earth is like a hard-boiled egg you’ve broken but not peeled, the shell has broken up into different sized pieces. Earth’s thin crust is much like the shell of an egg, extremely thin relative to the interior of the Earth.
A view of Earth’s internal structure and their relative sizes. The earth’s interior is divided into the inner core, outer core, mantle, and crust. The crust is sometimes referred to as the lithosphere, and the upper part of the mantle is referred to as the asthenosphere. The two enlargements give you a sense of the size of the crust and upper mantle. (Earth Pearson/Prentice Hall)