Geology and Earth Resources By: Michela Griffin

Earth as a Layered Sphere Core: Interior of the earth; composed of a dense, intensely hot mass of metal that is thousands of kilometers in diameter; contains metal Surrounding the core is the mantle: Less dense than the core; contains oxygen, nitrogen, magnesium Surrounding the core is the mantle: Less dense than the core; contains oxygen, nitrogen, magnesium Outermost layer of earth is the crust: cool, lightweight, outermost layer of the earth’s surface that floats on the soft underlying layers- where the seafloor and continents are

Tectonic Processes The upper layer of the mantle has convection currents that break the overlying crust in huge blocks called Tectonic Plates: Huge blocks of the earth’s crust that slide around slowly, pulling apart (diverge) to open new ocean basins or crashing into each other (converge) to create new, larger landmasses When an oceanic plate collides with a continental landmass, the continental plate will ride up over the seafloor. Continents drift together  giant landmass (i.e. Pangaea)

Techtonic Processes (cont.) Earthquakes are caused by grinding and jerking as plates slide past each other or as they converge or diverge Mountain ranges are pushed up at the margins of colliding plates (i.e. Himalayas- Indian subcontinent into Asia) Speed of processes vary- 1cm a year to 18cm a year

Rocks and Minerals Mineral: naturally occurring, inorganic, solid element or composed with a definite chemical composition and a regular internal crystal structure Most fundamental characteristics: 1) Chemical Composition and 2) Crystal Structure No 2 Minerals are the same Rock: solid, cohesive, aggregate of one or more minerals

The Rock Cycle The rock cycle includes a variety of geologic processes that can transform any rock

The Rock Cycle (cont.) Three major rock classifications: igneous, sedimentary, and metamorphic Igneous Rocks: The most common rock type; made by cooling magma Sedimentary rock is formed from the long-term deposit and compaction of sediments into rock. Metamorphic rock is rock formed when another type of rock is changed by pressure, heat, and tectonic processes. (i.e. limestone  marble)

IGNEOUS ROCK METAMORPHIC ROCK SEDIMENTARY ROCK

Weathering Mechanical weathering is the physical breakup of rocks into smaller pieces without changing the chemical composition. Chemical weathering is the selective removal or alteration of specific components that leads to weakening and disintegration of the rock

Economic Geology and Mineralogy Economic geology is the study of minerals that are heavily used in manufacturing and an important part of commerce. Metals have been very important in human affairs (i.e. Stone Age) Most economically valuable resources exist everywhere in small amounts Economic geology is the study of minerals that are heavily used in manufacturing and an important part of commerce. Metals have been very important in human affairs (i.e. Stone Age) Most economically valuable resources exist everywhere in small amounts

Metals & Nonmetals Metals consumed in greatest quantity: iron, aluminum, manganese, copper and chromium- produced mainly in mountainous areas Nonmetals (covers silicate minerals to sand, gravel, salts, etc.): durable, highly valuable, and easily portable i.e. Gemstones Sand and gravel production comprise by far the greatest volume and dollar value of all nonmetal mineral resources.

Environmental Effects of Resource Extraction Mining and purifying all of the mineral resources can have severe environmental and social consequences Can affect water quality: i.e. sulfuric acid is produced when gold and other metals are mined from sulfide ores- DANGEROUS Chemical substances can contaminate lakes and streams

Mining Placer mining- washing out metals deposited in the gravel of streambeds (i.e. gold)  destroys streambeds but fills the water with suspended solids that smother aquatic life Other types of mining: open-pit mining, strip mining, and underground mining Risk of fires: inaccessibility and size of the fires make many impossible to extinguish and control ‘Toxic Soup’ in metal mines can leak into lakes and endanger wildlife- 12,000 miles of rivers and streams in the U.S. are contaminated by mine drainage 1997 federal Surface Mining Control and Reclamation Act requires better restoration of strip-mined lands; but restoration is difficult because it is expensive

Processing Ores Metals are extracted from ores by heating or with chemical solvents- releases large quantities of toxic materials Smelting: roasting ore to release metals; major source of air pollution Heap-Leach Extraction: piling crushed ore in huge heaps and spraying it with a dilute alakine-cyanide solution; large water pollutant

Conserving Geologic Resources Recycling Metals are easily recyclable and require much less energy than extracting new metals (i.e. Aluminum) New materials can be substituted for old Using iron and steel replaced by polymers, aluminum, etc.

Geologic Hazards Earthquakes, volcanic eruptions, floods, and landslides and other catastrophic events, though rare, have shaped the earth significantly

Earthquakes can be very destructive Earthquakes are sudden movements in the earth’s crust that occur along faults where one rock mass slides past another one ‘Mysterious, sudden, and violent’ Worst death toll occurs in cities with poorly constructed buildings Most seismically active region in the U.S. is along the west coast where tectonic plates are colliding Tsunamis are giant seismic sea swells generated from the center of an earthquake. They are incredibly destructive to coastal areas.

Volcanoes Volcanoes and undersea magma vents produce much of the earth’s crust but release large volumes of ash and dust into the air  can block sunlight “Ring of Fire”- seismic activity and active volcanoes around the edge of the Pacific Ocean More than 500 million people live in the danger zone around volcanoes Nuees ardentes (glowing clouds) are deadly, denser than air mixtures of hot gases and ash like those that inundated Pompeii Mudslides are also dangerous

Landslides Mass wasting: geological materials are moved down slope from one place to another i.e. Rockslides and avalanches Over $1 billion in property damage is done every year by landslides in the U.S. Many human activities such as road construction and forest clearing increase the frequency and damage done by landslides

Works Cited Montgomery, C. W Environmental Geology (4 th ed.). Dubuque, IA: WCB/McGraw- Hill Co. Plummer, C. C., et al Physical Geology. Dubuque, IA: WCB/McGraw-Hill Co. Ripley, E. A., et al Environmental Effects of Mining. Delray Beach, FL: St. Lucie Press erences_16.mhtml erences_16.mhtml