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Earth Cross Section | Rocks | Rock Cycle | Minerals | Rare Earth Elements | Soil | Plate Tectonics | Glossary

Earth science (also known as geoscience) is an term used for multiple disciplines including Geology, Mineralogy, Geophysics, Oceanography, Atmospheric sciences, Biology and many sub-disciplines.

Earth Cross Section:
earth cross section, core layers, mantle The inner core is under such extreme pressure that it remains solid.
As the Earth rotates, the liquid outer core spins, creating the Earth's magnetic field.
Most of the Earth's mass is in the mantle, which is composed of iron (Fe), magnesium (Mg), aluminum (Al), silicon (Si), and oxygen (O) silicate compounds. The mantle is solid but can deform slowly in a plastic manner. Convection in the mantle drives plate tectonic motions of the sea floor and continents.
The upper part of the mantle and the crust form a rigid layer of rock called the lithosphere, is which broken up into the moving plates that contain the world's continents and oceans.
Earth's Interior at UNR

Rocks are hard objects composed of single mineral or more typically a aggregate of minerals. See Minerals below.
They are classified based on how they are formed.
  • Igneous rocks: formed by the cooling and hardening of magma (molten rock).
    - Magma that cools underground and is exposed by erosion:
    It cools much more slowly and thus allow ample time to sustain crystal precipitation and growth, resulting in the formation of coarser grained, nearly completely crystalline, igneous rocks.
    E.g. gabbro, granite (quartz, feldspar, mica, and usually hornblende)

    - Lava from a volcano that cools on the surface:
    E.g. Pumice, Obsidian, basalt (45-54 % silica [SiO2]), pumice, rhyolite

    Source: Volcanic rocks at USGS.gov
    See also: CVO Website - Igneous Rocks
    Volcanoes here.

  • Sedimentary rocks: formed by the compaction and cementing of layers of sediment:
    - Rock fragments - sand, silt and clay
    - Plant and animal remains
    - Minerals - Quartz, Feldspars, Micas (Silicon and Oxygen), Calcite and Dolomite CaMg(CO3)2, ...
    E.g. sandstone, shale, chert, some limestones (CaCO3)
  • Metamorphic rocks: formed by the effect of heat and/or pressure on other rocks
    - limestone (sed.) > marble
    - granite (ign.) > gneiss
    - shale (sed.) > slate > phyllite > schist
    - sandstone > quartzite
Rock Cycle:
Rocks are recycled from one type to another by forces such as plate tectonics and weathering.

Classification of volcanic rocks is by the proportion of light and dark minerals.
Rock type Silica content Colour Examples
Felsic > 65% light rhyolite, granite
Intermediate 55-65% Intermediate Andesite, dacite, diorite, granodiorite
Mafic 45-55% dark basalt, gabbro
Ultramafic < 45% Dark Peridotite
Source: Lava composition and volcanic rocks at RockCollector.co.uk

Types of volcanic rock:
Magma, Lava, Lava Flows, etc. at vulcan.wr.usgs.gov
Debris Flows, Mudflows, Lahars - Lahars can form in a variety of ways, either during an eruption or when a volcano is quiet.
They contain a high concentration of rock debris and resemble broken concrete when cooled.
Rock Key at RockHounds.com
How Rocks Form at SchoolWorkHelper

lbs / cu ft
Type EngineeringToolBox Simetric
low hi
Basalt/Traprock 150 190 188
Brick 87 143 120-150
Concrete 75 150 148
Granite 165 172 168
Limestone 167 171 163
Marble 160 177 160
Sandstone 134 147 145
Slate 162 205 168
Gravel 95-105
Sand dry 100
Sand wet 120
Earth, loose 75 78
Earth, rammed 100 125
Ice solid 57
Ice Crushed 37
Water 62

Except for native elements, minerals are salts composed of positively charged cations (e.g. K+, Na+, Ca++, Fe+++) and negatively charged anionic groups (e.g. CO3, PO4).
Feldspars (KAlSi3O8 - NaAlSi3O8 - CaAl2Si2O8)is the most abundant mineral.
Quartz (SiO2) is second.

Single element minerals: Copper, Graphite (Carbon), Diamond (Carbon), Sulphur, Silver and Gold.

Mineral Families at uwsp
Rocks and Minerals Dictionary: - EnchantedLearning.com

Rare Earth Elements:
Modern technology (smart phones, laptops, batteries in hybrid vehicles and cordless tools, night vision goggles) all use rare earth elements.

They're actually metals, and they aren't really rare; they're just scattered. 97% come from Chine, but in 2011 Japan discover them under the Pacific near Hawaii.

- Neodymium - Magnets in wind turbines, cordless tool motors, sound systems, cell phones.
- Lanthanum and neodymium - nickel metal hydride batteries used in hybrid cars like the Toyota Prius.
  Lanthanum is also used for Lithium Ion batteries used in hybrid cars like the Ford focus and Hyundai Sonata.
  and petroleum refining.
- Indium - Solar cells and flatpanel displays.
- Cerium and lanthanum - Catalytic converters in auto exhausts
- Yttrium - Yttrium based materials improve the fuel efficiency of auto engines. Also used in microwave communications devices. - Scandium - Aluminum-alloy baseball bats See:
REE - Rare Earth Elements and their Uses at geology.com
Rare Earth Elements - From National Geographic Magazine

An average soil sample is 45 percent minerals, 25 percent water, 25 percent air, and five percent organic matter.
Different-sized mineral particles from eroding rocks, such as sand, silt, and clay, give soil its texture.
Fungi and bacteria help break down organic matter in the soil.
Natural processes can take more than 500 years to form one inch of topsoil.

What on Earth is Soil? | Kid's Stuff | US EPA

Plate Tectonics:
plate tectonics earth plates
plate subduction As plates collide one plate tends to move under the other and the friction causes for formation of magma causing volcanoes. Scientist are still debating whether the magma is generated by the partial melting of the subducted oceanic slab, or the overlying continental lithosphere, or both?
As plates move side by side as the Pacific plate moving north and the North American plate moving south you get earthquakes.

This Dynamic Earth - The Story of Plate Tectonics at USGS
Fault Zones - Northern California

Distance to the horizon:
Glossary of Terms:
Alpine Lake - lakes or reservoirs at high altitudes, usually starting around 5,000 feet

Brook: A small natural stream of fresh water smaller than a creek. 1
A primary stream not formed by tributaries, though often fed below its source, as by rills or runlets.

Clay: Composed primarily of fine-grained minerals. A subtype of phyllosilicate minerals composed of Aluminum (Al) Silicone (Si) and Oxygen (O) and other minerals. Clays have smaller particles < 2 µm.
Depending on the content of the soil, clay can appear in various colors, from a dull gray to a deep orange-red.

Clay Soil: a soil containing more than 40% clay, but less than 45% sand, and less than 40% silt.

Creek: A small bending or winding stream that is often shallow or intermittent; a rivulet. Smaller than a stream larger than a brook.1

Estuary: the area where the fresh water of a river meets and mixes with the salt water of the ocean.

Glacial Lake - a lake with origins in a melted glacier.


Lake: The definition is subjective.
Early limnologists in the late 18th, early 19th centuries attempted to define the transition from a lake to a pond in various ways. Area, depth or both were an essential part of most definitions, but what area or what depth differed. Some used thermal stratification.
Limnologists today recognize that nature canÕt be divided into precise, neat categories and accept the fact that there will never be a precise definition.
Source: New Hampshire Department of Environmental Services

1. Most of its area is too deep (> 6 ft) for plants to grow on the bottom.
2. A lake is fed by rivers or streams. A pond is created by ground water.
3. Size
5 acres - University of Liverpool
20 acres (1/4 mi x 1/8 mi) Washington Environmental Permitting
Limnology: The study of inland waters

Loam: Soil composed of sand, silt, and clay in relatively even concentration (about 40-40-20% concentration respectively).

Mountain: A large landform that stretches above the surrounding land in a limited area usually in the form of a peak. A mountain is generally steeper than a hill. There is no universally accepted definition of a mountain. Various definitions have been proposed with heights from 300 m (984 ft) to 2,500 m (8,202 ft).
See mountain at wikipedia

Ocean: A major body of saline water. Oceans cover approximately 71% of the earth's surface. Pacific, Southern (extension of Pacific), Atlantic, Indian, and Arctic.

Pond: The distinction between a pond and lake is subjective.
Washington state defines a pond is a body of still fresh or brackish water shallow enough for sunlight to reach the bottom, allowing rooted plants to grow anywhere across its area.

Reservoir: An artificial (man made by the construction of a dam) lake that is used to store water.

River: A fairly large, moving body of fresh or brackish water that travels within a channel. I couldn't find any official definition distinguishing a stream from a river.1

Sand: Soil particles between 0.05 and 2 mm in diameter.

Silt: A granular material of a size somewhere between sand and clay derived from soil or rock. Silt may occur as a soil or as suspended sediment in water.

Stream: Organically shaped channel, moving water from one location to another following a defined shape in a natural or artificially altered environment; small river; a steady flow of water.1

Talus: A sloping mass of rocky fragments at the base of a cliff.

Tributary: A stream or river that flows into a larger stream or river.

Vernal Pool: Seasonal depressional wetlands that occur under the Mediterranean climate conditions of the West Coast. They are covered by shallow water for variable periods from winter to spring, but may be completely dry for most of the summer and fall.

Watershed: The land area that drains water to a particular stream, river, or lake. It is a land feature that can be identified by tracing a line along the highest elevations between two areas on a map, often a ridge. Large watersheds, like the Mississippi River basin contain thousands of smaller watersheds.

1. I couldn't find any official definitions of streams. Stream is sometimes used as a generic term to cover anything from a brook to a river. Other times they are defined by size with no official flow rate or other measurement. By size they go from brook to creek to stream to river.
See streams.

Other Glossaries:
Glossary at environmental permitting in Washington state
Glossary of Terms at GeoSyntec Consultants
Glossary: stream related terms at StreamNet.org
USGS Water Science Glossary of Terms
Waters by Type | Our Waters | US EPA
Types of Water Bodies | Lake Scientist

Earth science - Wikipedia

   Earth History
   Earthquakes | Volcanoes
   Tahoe geology
   Mountain Ranges
 Atmospheric science (Climatology, meteorology)
 Water Science: Oceanography & Hydrology (limnology)
 Soil science  (Biogeochemistry)
Rocks and the Rock Cycle at ScienceViews.com
USGS Photo Glossary of volcanic terms
Granite Information
Earth Sciences and News at Earth Pages
Water Science: Oceanography & Hydrology Scholarly Societies
EPA Western Ecology Division
Cross section:
Rock cycle, how rocks and minerals are formed, MineralTown.com
The University of the State of NY - Regents High School Examination - Earth Science (http://www.nysedregents.org/EarthScience/113/esci12013-exam.pdf)
Climate Change / Global Warming

last updated 31 July 2011