subject: Earth's Engine and the Rock Cycle [print this page] Earth's Engine and the Rock Cycle Earth's Engine and the Rock Cycle
The interior of the earth is full of energy too, and it also gives off energy. Life on earth survives because of a careful balance between solar energy and the energy from inside the planet.
The structure of the planet
It's 4,000 miles to the center of the earth. It's impossible for us to get there. The deepest hole that's ever been dug only goes 7.5 miles deep. Since we can't see or go to the interior of the earth, scientists use indirect evidence to study the earth. Our current theory is based on this indirect evidence.
1. The inner core is solid, iron, spherical, and if you could miraculously get into the center of it, you'd be in a zero gravity zone. It's estimated that the inner core is 12,000 degrees.
2. The outer core is liquid and bigger than the moon. It also is made of iron. It rotates and generates a magnetic field. The outer core is estimated to be bigger than the moon and at a temperature of 3,000 degrees.
3. The mantle is a flowing solid. (To wrap your head around that, envision red-hot iron and how it is solid but can change shapes.) The mantle has plumes that occasionally break through the surface forming hot spots and hot-spot volcanoes. The mantle also has slow convection cycles.
4. The crust is the part of the earth we live on. It's 30 miles deep, but no one has ever made a hole deeper than 7.5 miles. It's rocky. The crust sort of floats on the surface of the mantle. The crust is broken into pieces called tectonic plates. The plates move as they "float" on the mantle.
Since the plates are floating they sometimes go away from each other, toward each other, and some slip past each other. Each type of movement has a different name.
1. Convergent: The plates come toward each other.
2. Divergent: The plates separate away from each other.
3. Transform: The plates slide against each other.
Convergent plates move toward each other. As they come together, the heavier one goes under the lighter one. Oceanic plates are heavier than continental plates. As one plate is subducted, the other plate grows a mountain. Divergent plates go away from each other. The empty space is filled with mantle, which cools to make new crust. Transform plates slip by each other.
Why did we learn about the earth?
Igneous rocks are formed when the magma of the mantle cools and forms rocks. The substance of the mantle is called magma when it is under the earth. It's called lava when it is above.
Igneous means "of fire"
Igneous rocks are made when magma cools. Some ways magma can form rocks are from divergent plates, or seafloor spreading, and when volcanoes erupt.
There are two categories for igneous rocks. Intrusive igneous rocks cool under the ground. They cool slowly, so they have grains that are more coarse. Extrusive igneous rocks cool above the ground. They cool fast, so they have small grains. Igneous rocks weather over time. They can turn to dust, crack, or change chemically when they react with water and air.
Sedimentary rocks are created in two different fashions. (Three if you include organic methods.) Clastic sedimentary rocks are formed by layers of rocks being compressed. Chemical sedimentary rocks form by precipitating out of a solution.
Metamorphic rocks form when igneous or sedimentary rocks are subjected to intense heat, pressure, or chemical changes.
The rock cycle is the process of igneous rocks being formed, those igneous rocks eroding and weathering into sedimentary rocks, and pressure, temperature, and chemical changes that turn the rocks into metamorphic rocks. Any of the rocks, igneous, sedimentary, and metamorphic can be subducted back into the mantle and changed into magma.
Gwen Nicodemus has two children that she's been homeschooling all their lives. Gwen also teaches science and math classes in a local homeschooling cooperative. As a temporarily retired engineer, Gwen keeps her brain active by writing unit studies and little books for her kids whenever someone gets interested in a new topic. Check out the great free resources, including unit studies, videos, tutorials, and little books at http://UnitStudiesByGwen.com
