Page 39 - Curriculum Visions Dynamic Book

The whole of the Earth is dominated by just a few chemical elements: iron, oxygen, silicon, and magnesium. Together they account for over nine-tenths of the mass of the planet.
Oxygen is the reactive key element. By combining with silicon, it makes silicates, such as quartz, and the minerals in rocks, such as granite. By combining with aluminum as well (a relatively common element in the crust but almost absent elsewhere in the Earth), minerals such as feldspars and soils such as clay are formed.
In the mantle silicates linked with iron make the minerals that form rocks, such as gabbro and basalt. In contrast to the rocks of which the crust and the mantle are formed, the core is probably made of iron, with smaller amounts of oxygen and sulfur.
When we realized that the Earth has a different chemistry in its inner and its outer regions, we could figure out how the other planets emerged.
The difference between surface and core chemistry comes about because of differences in heat and pressure, which both increase toward the center of the Earth.
Interestingly, the core of the Earth, at 7,500°C, is hotter than the surface of the Sun. This heat, together with warmth produced as radioactive elements decay within the Earth, provides the energy that powers the movement of the plates and the production of volcanoes.
 Volcanic eruptions, such as Mt. Etna in
the Mediterranean,
do not just release ash and lava and build the Earth’s crust; they also release large amounts of water as vapor and a range of other gases. Such outpourings created the first atmosphere and still contribute to it.
The central region of a body.
The solid outer surface of a rocky body.
earthqUake The shock waves produced by the sudden movement of two pieces of brittle crust.
element A substance that cannot be decomposed into simpler substances by chemical means.
magnetic field The region of influence of a magnetic body.
mantle The region of a planet between the core and the crust.
mass The amount of matter in an object. mineral A solid crystalline substance.
plastic The ability of certain solid substances to be molded or deformed to a new shape under pressure without cracking.
plate A very large unbroken part of the crust of a planet. Also called tectonic plate.
radioactive The property of some materials that emit radiation or energetic particles from the nucleus of their atoms.
seismic Shaking, relating to earthquakes.
volcano A mound or mountain that is formed from ash or lava.
core crUst
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