G103
Week One
Earth Materials
Lecture Highlights
and Exercises
The Composition of the Earth
The Earth is composed of various types of building blocks.
One way of looking at the composition of the Earth is to look at the spectrum of materials.
Ions ---- Molecules ---- Minerals ---- Rocks
Ions and atoms are the smallest subdivision we commonly use for earth materials.
Ions and atoms are single elements (like oxygen or hydrogen) that are composed of a nucleus containing protons and neutrons, and shells of electrons around them. An atom has a balanced or neutral charge and an ion has a positive or negative charge.
Molecules are groups of ions bonded together to form a chemical compound. Water is an example of a molecule. An individual molecule may not be stable on it own, but can become a stable substance when a number of molecules are present...like water or plastics.
There are two common types of chemical bonds found in earth materials. Ionic bonds are formed by the electrical attraction between two ions of opposite charge.
Covalent bonding occurs when two atoms share electrons.
When a group of ions or molecules form a solid structure, called a lattice, a mineral compound may form.
Put on your 3D glasses and click on the link below.
Molecular Structure of Silicates
A mineral is defined as a naturally occurring, crystalline, inorganic material with a specific range of chemical composition and an regular internal order of atoms.
Minerals form all of the major materials on the surface of the Earth.
Minerals ...... Rocks ....... Soil ...... Sediment
Click on the link below to hear a mini-lecture audio segment.
The Formation of Minerals
Minerals form by crystallization from a molten liquid or from water. The mineral forms in a regular and predictable fashion that is related to its internal structure and composition.
When minerals group together in various ways, they form rocks, sediment, or soil. Minerals of the same type or minerals of different types can combine to form rocks.
The chemical composition of the earth and the crust of the earth are shown below.The composition of the crust, or surface of the earth is similar to the rock granite.
Plate Tectonics
Plate tectonics is arguably the most important scientific revolution of the 20th century. It is so compelling because it provides and explanation for practically all of the things we observe on the surface of the earth, and those processes that we observe originating below the surface of the Earth. The earth is covered with 14 major plates that move around the surface of the Earth and have done so for over 500 million years.
The tectonic plates along the surface of the earth control most of the processes and materials we observe on the earth. The movement and interaction of the plates are key factors in forming almost any rock or structure we observe. The movement of tectonic plates is shown below.
The Rock Cycle
Rocks and the Rock Cycle
The Earth is composed of three different rock types: igneous, sedimentary, and metamorphic.
Igneous Rocks
- Igneous rocks form when a molten magma (melted rock) cools and crystallizes.The name igneous is derived from the Latin word “ignis”, which means from fire.
Sedimentary Rocks
There are two types of sedimentary rocks, chemical and clastic.
- Chemical sedimentary rocks form by precipitation of minerals from an aqueous solution or by some other chemical or biochemical reaction.
- Clastic sedimentary rocks form when existing rocks are weathered into small fragments called sediment, eroded and transported to another site, and deposited, compacted and lithified.
Metamorphic Rocks
Metamorphic rocks are the result of the application of heat, pressure and directed stress, or some combination of these effects applied to pre-existing rock of any type. The process by which metamorphic rocks are produced is called metamorphism.
There are three types of metamorphism Regional, Dynamic and Contact.
The Rock Cycle
Rocks are in a constant process of transition from their current states and rock type classifications to the next phase of their existence as another rock type. The rock cycle is essentially a road map that allows us to follow the sequence of processes by which rocks from each of the three major rock types are formed from members of the other rock types.
