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There are three main classifications of rock. These classifications, determined by how the rock forms, include: igneous, metamorphic, and sedimentary rocks. The matter that makes up these rocks is the same matter that has always existed on Earth. It continues to be recycled, which is why the rock cycle is called a cycle.

A metamorphic rock is formed when any type of rock undergoes enough heat and pressure to bake the rock without actually melting it. The rock undergoes a chemical change due to the increased heat and pressure. That means that a chemical reaction has occurred making the substance something entirely new.

A sedimentary rock is formed when weathering breaks down any type of rock into smaller pieces called sediments. These sediments are eroded, or moved, by wind, water, animals, etc. where they are deposited and can accumulate. Over time they begin to compact and cement forming a solid rock made of sediments, or bits of smaller rocks. Typically these rocks are formed at the bottom of a large body of water. Florida, for example, has large areas of sedimentary rock layers, indicating that it was once covered by water.

Lastly, igneous rocks--rocks of fire--are formed when any rock is melted into molten rock and then cooled into solid rock. This is caused by volcanic activity.

See the model below which demonstrates this ongoing cycle and the processes that change rock from one type to another.

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There are three types of boundaries: convergent, transform, and divergent. The boundary type describes the way the plates are moving in relation to each other at the boundary, or the area where the plates meet. Convergent describes an area where plates move together. Divergent describes and area where plates move apart. And, lastly, transform describes and area where plates slide past each other. See the picture below.

The reason these plates move at all is because of something called convection within the mantle. The movement of material is being caused by heat flowing through it and changing densities that make the material rise and sink. The type of heat transfer that causes this is called convection. That's why the movement of the material is called "convection currents." In diagrams these will often be represented by cyclical arrows showing how mantle rock is rising and falling over and over again. (See review on heat transfer for more information).

As the plates move towards, apart, or past each other we get different features or events on the surface. While volcanoes and earthquakes can happen anywhere on Earth's surface, they will happen more frequently at a boundary. At convergent boundaries, there tends to be a subduction zone if one piece of crust is denser than the other. The density makes it sink lower and back into the mantle. Where this happens pressure and heat where the plates are moving against each other creates chambers of magma that can erupt as volcanoes (volcanic arcs) either on oceanic or continental crust. Where plates collide and there is little difference in density, mountains will form as rock folds together.

At a divergent boundary, plates are moving apart from each other. This forms a rift. But, its not like hole into the Earth's mantle. Rather, magma seeps up to fill the area. Sometimes this pressured magma forms underwater mountains called ridges along the boundary of two oceanic crustal plates.

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The states of matter that we have reviewed in class are solids, liquids, gases, and plasma. The state of matter is determined by the motion and spacing of molecules. When these molecules speed up they move farther apart and gain more energy turning it into a different state. When energy is removed from these molecules they slow down and clump together forming a different state of matter.

The properties of different states of matter differ depending on the amounts of energy the molecules produce. The properties of soilds are that they have molecules with very little energy, the keep their form/shape, the molecules are touching/close together, they are vibrating. A liquid is a substance with molecules that can flow past each other, the molecules are close enough to see the substance, they take the shape of their container, and they are hard to compress. Gasses have a lot of energy, they move farther apart and more quickly than liquids and gases. They do not have a definite shape or size, they will expand to fill their container.

As molecules gain heat, they speed up and move farther away, this makes the material have a lower density, which makes it rise above material with a higher density. As it rises, it passes on the thermal energy to other molecules int he fluid and they rise too. As the molecules lose energy, their density increases and the opposite happens.
We believe that the state of matter in each of the 4 main layers of our earth is
solid. We sometimes say that evaporation and vaporization are the just describing the change between a liquid to a gas because they both describe the adding energy and changing to a gas.

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The four main layers of the Earth are the inner core, outer core, mantle, and crust. The inner core is extremely hot and is made of solid iron and nickel. The outer core is made of a sea of iron and nickel and can go up to 6000 Celsius. The mantle is the thickest layer and is made of hot semi rock. The crust is the thinnest layer. It's made of basalt and granite.
Continental crust is less dense and thicker than oceanic crust, which is more dense and thinner.
The density increases as the layers get closer to the core. The crust being the least dense, and the inner core is the most dense.
The  asthenosphere is a soft, yet solid layer on which plates can "flow" which is in the center part of the mantle. The lithosphere is the crust and upper most mantle. It's made of rigid rock layer divided into tectonic plates.
Convection currents happen because heat from the core is driving convection currents in the mantle. There is convection currents in the mantle because the lithosphere has tectonic plates that ride on the hot solid rock of the mantle.
The magnetic field is important to life on Earth because it blocks the solar winds.

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A force is any push or pull on an object. There are two types of forces, contact forces, and non-contact forces. A contact force is a forces that moves something by directly touching it, and a non-contact force is when an object is moved but it is not being physically touched. For example a contact force could be friction, and a non-contact force could be magnetism. There are a few special types of forces like gravity, which is a non-contact force,  we refer to it as weight because the more gravity there is the more we weigh, and the less gravity there is the less we weigh. The more mass you have the more gravity acts upon you, it speeds you descent after something like a jump. The farther you are from our planet Earth the less the gravity will effect you. Speaking of gravity, that brings up fields. Gravity has it's own field, but what is a field exactly? A field is the surrounding area of say, a magnet, the field is the area around the magnet that it's force will act upon.

One type of force is a normal force, a normal force you can see every single day of your life, a normal force is the force of the floor pushing up on your feet. You can create an applied force by walking up to a desk, and simply pushing it. An applied force is any force that a person creates by pushing or pulling something. If you were actually pushing or pulling that desk you would create friction. Friction is that force on the ground that stops a ball from rolling. Some materials have high friction, like sand paper, and some have less friction, like ice. Scientist have a term for when lot's of forces are acting on one object, it's called a net force.

Say you have a hanging light on your ceiling, there are two forces acting on it, gravity, and tension. That light might fall however, if it becomes unbalanced. It could become unbalanced by cutting the rope. An unbalanced force is when there are two forces acting against one another, but instead of being balanced out and just being neutral, one force is stronger and the object starts into motion.

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Thermal energy flows from warmer objects to cooler objects, through three different ways.
One way is conduction, the transfer of heat through physical contact. One example would be a spoon heating up in a hot pot of soup. Radiation is a transfer of energy through empty space. For instance radiation enables sunlight to warm Earth's surface. Convection is the transfer of heat through the movement of a heated fluid.  Convection occurs throughout the soup starting warm at the bottom, cooling of and rising to the top, forming a convection current.

Heat moving through the outer core and the mantle is caused by convection currents throughout both of the liquid layers.
When the convection currents move throughout these layers, the fluid pushes up, causing the plates to stir.
Cool fluids sink because they are more dense than hot fluids that rise, because of their low density.
The source for convection the inside of Earth's interior is the inner core. The source of energy for the convection outside the Earth's interior is our sun.