Transcript Rocks and Minerals

Rocks, Minerals,
Mining
Rocks and the Rock Cycle
The rock cycle is the constant formation and
destruction of rock
The rock cycle recycles scarce minerals and
elements
Rocks
Rocks are any solid mass of mineral or minerallike matter occurring naturally as part of our
planet
Types of Rocks
1. Igneous rock is formed by the crystallization
of molten magma
a. Intrusive form within the earth
b. Extrusive form when magma cools above the
earth’s surface
Rocks
Types of Rocks
2. Sedimentary rock is formed from the
weathered products of preexisting rocks
that have been transported, deposited,
compacted, and cemented.
3. Metamorphic rock is formed by the
alteration of pre-existing rock deep within
Earth (but still in the solid state) by heat,
pressure, and/or chemically active fluids.
Rock Cycle
Rock Cycle
Energy That Drives the Rock Cycle
1. Processes driven by heat from the Earth’s
interior are responsible for forming both
igneous rock and metamorphic rock
2. Weathering and the movement of
weathered materials are external processes
powered by energy from the sun.
3. External processes produce sedimentary
rocks
Minerals
Definition of a Mineral
1. Naturally occurring
2. Solid substance
3. Orderly crystalline structure
4. Definite chemical composition
5. Generally considered inorganic
Minerals
How Minerals Form
1. Crystallization from magma
2. Precipitation
3. Pressure and temperature
4. Hydrothermal solutions
WEATHERING & EROSION
Physical Weathering
The mechanical breakdown of rocks and
minerals
Can be caused by:
• Water, wind, temperature variations
• Biological agents such as roots
Bottom line: more surface area for chemical
weathering
Chemical Weathering
Breakdown caused by chemical rxns, and/or
dissolving of elements from rocks
Can be caused by:
• Naturally occurring acids
• Lichens produce acid to break down rock
• Anthropogenic: acid rain
Erosion
The physical removal of rock fragments (sediment,
soil, etc)
A result of 2 mechanisms:
• Physical: wind, water, ice
• Biological; burrowing animals
Erosion is a natural process
DISTRIBUTION OF MINERAL
RESOURCES
Surface Mining
Strip mining:
• Removal of “strips” of soil and rock to expose
ore
• Large volume of material is removed, resource
extracted and the tailings are returned
Surface Mining
Open-pit mining:
• Creation of a large pit; resource close to sfc, but
extends
• Copper mines
Mountaintop removal
• Uses explosives to remove the entire top of a
mountain
• Tailings are often deposited in lower elevations
(rivers and streams)
Surface Mining
Placer Mining
• Process of looking for minerals in river
sediments
• California gold rush
Subsurface Mining
If mineral resource is more than 100m below sfc
• Begins with horizontal tunnel
• Vertical shafts are drilled
• Deepest mines on earth – 3.5 km
Mining Safety and the Environment
Environment:
• Soil erosion
• Waterway damage
• Habitat fragmentation
• Pollution from tailings
• Groundwater & stream damage (mountaintop)
• Placer mining uses toxic metals (Hg)
• Acid mine drainage (pumped out of tunnels)
Mining Safety and the Environment
Safety:
• Subsurface mining is dangerous
• Explosions
• Accidental burial
• Fires
• Respiratory diseases (e.g. black lung disease)
Mining Legislation
Mining Law of 1872
• Regulate mining of Ag, Cu, Au ores and fuels on
federal lands
• Written to encourage development and
settlement of west
Surface Mining Control & Reclamation Act of 1977
• Mandate: minimal disturbance of land during
mining and reclaimed after