ENV 1301: Lithosphere

Radon prevention

Modern homes can be built to resist infiltration of radon gas.

Radon detection

Homeowners should buy and use radon detection kits.

Layers of Earth

Lithosphere (crust) → upper mantle (asthenosphere) → lower mantle → outer core (molten iron and nickel) → inner core (solid iron).

Lithosphere

Crust plus uppermost mantle; brittle, strong, rigid rock forming tectonic plates that float on weaker layers below.

Upper mantle

Asthenosphere; denser, partially melted, weaker rock layer providing buoyancy for tectonic movement.

Crust

5–70 km thick, makes up about 1% of Earth; thinner under oceans, thicker under continents.

Upper mantle size

Extends about 600 km deep, about 10% of Earth’s volume; uppermost 100 km forms end of lithosphere; asthenosphere extends 250 km.

Lower mantle

Extends to 2,900 km deep, about 45% of Earth’s volume; heat and pressure cause rock to act plastically.

Outer core

Molten iron and nickel extending to about 5,150 km deep.

Inner core

Solid iron or iron-nickel alloy, extends to Earth’s center at 6,371 km (3,950 miles).

Deepest human drilling

12.2 km (40,000 ft) in 1989 via Kola Superdeep Borehole in Russia.

Borehole goal

To drill as far into the Earth’s crust as possible.

Borehole comparison

Deeper than the Mariana Trench, taller than Mount Everest.

Borehole limits

Increasing temperature (180°C) and pressure degrade drill bits and create ductile rock layers that halt progress.

Inner Earth evidence

Seismic waves reveal structure based on speed and reflection patterns.

Seismograph

Instrument that records vibrations from earthquakes as seismograms.

Magnetic field

Generated by movement of molten iron in the outer core.

Rock samples

Rare materials like xenoliths and ophiolites offer physical samples from mantle or oceanic crust.

Xenolith

Rock fragment trapped inside another rock, often carried up by magma.

Ophiolite

Section of oceanic crust or upper mantle thrust upward by tectonic movement.

Plate tectonics

Heat from Earth drives convection currents that move lithospheric plates 2–15 cm per year.

Crust composition

About 15 major plates move slowly, reshaping Earth’s surface.

Tectonic results

Builds mountains, forms oceans, islands, and continents, and causes earthquakes and volcanoes.

Tectonic history

Original supercontinent separated and continues to shift today.

Divergent plate boundary

Plates move apart as magma rises and forms new lithosphere.

Transform plate boundary

Plates grind sideways along faults, causing earthquakes.

Convergent plate boundary

Denser plate subducts beneath the other or both continental plates collide to form mountains.

Subduction

Older or denser oceanic crust dives under another, creating trenches or volcanic arcs.

Continental collision

Two continental plates push together, folding and uplifting to form mountain ranges.

Tectonic hazards

Earthquakes and volcanoes occur mainly along plate boundaries.

Ring of Fire

Circum-Pacific belt where 90% of earthquakes and volcanoes occur.

Earthquake

Sudden energy release along faults, can cause landslides and tsunamis.

Magnitude

Energy at the earthquake’s source measured by Richter scale.

Intensity

Observed surface effects, including shaking and damage.

Volcano

Opening where molten rock, ash, or gas escapes to the surface.

Volcanic zones

Often located in subduction areas of convergent boundaries.

Volcanic effects

Can build new mountains, islands, and geological layers.

Volcanic activity

Japan has about 100 active volcanoes, 10% of the world’s total.

Supervolcano

Exceptionally large volcano capable of massive eruptions, like Yellowstone.

Pyroclastic flow

Fast-moving avalanche of ash, rock, and gas traveling 60–430 mph.

Caldera

Bowl-shaped depression formed when a volcano’s summit collapses after an eruption.

Archipelago

Group of volcanic or continental islands often formed by tectonic or volcanic activity.

Atoll

Ring-shaped reef or island surrounding a lagoon.

Lagoon

Shallow body of water separated by a reef or sandbar.

Atoll location

Mostly in the Pacific Ocean; few in the Atlantic.

Example

Diego Garcia, largest island of the Chagos Archipelago, British territory transferred to Mauritius.

Volcanic mountain range

Formed when subduction occurs beneath a continental plate.

Example range

Cascade Range includes both volcanic and non-volcanic mountains.

Mt. St. Helens recovery

Species like deer mice, pocket gophers, and prairie lupine led regrowth.

Recovery process

Underground organisms and small plants helped ecosystem rebound.

Recovery timeline

Natural regrowth took about 40 years, from 1984 to 2013.

Hydraulic fracturing

Process of injecting high-pressure water, sand, and chemicals to extract oil or gas.

Fracking water use

Consumes large volumes of water compared to other industrial uses.

Fracking contamination

Leaks or fractures in wells can pollute groundwater.

Fracking and earthquakes

Deep wastewater injections can increase local seismic activity.

Methane pollution

Methane from production is more harmful than CO2 but stays in the atmosphere for a shorter time.

Fracking efficiency

Produces energy and profit but raises sustainability and replacement concerns.

Magma

Liquid rock formed at high temperatures beneath Earth’s surface.

Lava

Magma that erupts and reaches the surface.

Igneous rock

Rock formed when lava or magma cools and solidifies.

Sediments

Particles produced by weathering or erosion of rock by wind and water.

Sedimentary rock

Rock formed from accumulation, burial, compaction, and cementation of sediments such as sand, mud, or organic matter.

Metamorphic rock

Rock changed by heat and pressure that alters its physical properties.

Rock cycle

Continuous process of heating, melting, cooling, breaking, and reassembling rocks and minerals.

Mountain composition

Depends on depth, layers, and type of mountain.

Mt. Everest

Made mostly of sedimentary rock.

Sierra Nevada Batholith

Composed of igneous granite formed from cooled magma.

Batholith

Large mass of igneous rock formed deep underground.

Rock

Solid aggregation of one or more minerals, such as sandstone, limestone, granite, or basalt.

Mineral

Naturally occurring element or compound with a crystal structure and specific chemical and physical properties, such as feldspar, mica, quartz, or calcite.

Mining

Extraction of minerals or other resources such as oil and water from the ground.

Ore processing

Ore is pulverized, washed, and smelted to remove impurities.

Smelting

Heating and chemically treating ore to extract metal or create alloys.

Alloy

Mixture of one metal with another metal or non-metal to form a new substance.

Steel

Alloy of iron and carbon; stainless steel adds chromium.

Bronze

Alloy of copper and tin.

Brass

Alloy of copper and zinc.

Alloy benefits

Strength, heat resistance, and corrosion resistance.

Tailings

Portions of ore left after metals have been extracted, often stored in large reservoirs.

Tailings pollution

Can contaminate soil and water.

Surface impoundments

Reservoirs used to store mining waste; leaks or wall failures cause large spills.

Impoundment risk

Small-scale leaching and contamination from poor lining or maintenance.

Other pollution

Includes particulate matter, noise, seismic waves, and land subsidence.

Strip mining

Removes surface soil and rock in layers to expose shallow, horizontal mineral deposits.

Strip mining process

Strip is refilled with overburden before miners move to the next area.

Acid mine drainage

Occurs when sulfide minerals react with oxygen and water to produce sulfuric acid, which contaminates waterways and leaches metals like iron, turning water orange.

Subsurface mining

Involves digging shafts and tunnels deep underground to access minerals.

Subsurface risks

Explosions, collapses, coal dust, and toxic gas exposure.

Post-mining issues

Abandoned mines cause acid runoff and surface sinkholes.

Centralia example

Town abandoned after underground mine fires continued burning.

Open pit mining

Involves digging a large terraced pit to access widely spread minerals.

Open pit use

Used when ore is evenly distributed in rock formations.

Quarry

Open pit used for clay, gravel, sand, or stone.

Bingham Canyon Mine

World’s largest man-made hole, located in Utah.

Mountaintop removal

Blasting off the top of a mountain to reach underground mineral seams.

Mountaintop removal effects

Forests are clear-cut, topsoil removed, and excess rock dumped into valleys.

Environmental impact

Causes erosion, mudslides, flash floods, and ecosystem loss.

EPA response

Revoked permits and reexamined method across Appalachia.

Reclamation

Restoring mined land to original or usable condition after extraction.

Reclamation steps

Remove buildings, replace overburden, fill shafts, and replant vegetation.