Rocks and Fossils in Cinema

Plate Tectonics and Volcanos

Volcanoes form where tectonic plates pull apart, collide, or slide over superheated underground spots

Plate Tectonics and Earthquakes

Earthquakes occur when tectonic plates shift, jam, or break under intense pressure along cracks (faults)

Subduction

• When the continental crust and oceanic crust collide — cooler crust plunges into the mantle

• Oceanic lithosphere is more dense, so the ocean plate subducts into the mantle + begins to melt

• Magma rises, and volcanoes form on the continental plate

Layers of the Earth

1. Crust — thin + brittle

2. Mantle — thick + voluminous + mostly plastic deformation

3. Outer core — liquid

4. Inner core — solid (hot enough to be liquid but has high pressure)

Humans in Melt

Humans would not sink into it —> it is extremely dense compared to humans —> humans would float on top

Continental Crust

Less dense + older compared to oceanic crust

Oceanic Crust

Denser + younger compared to continental crust

Lithosphere

Includes crust + upper portion of mantle

Asthenosphere

Mechanically weak, ductile region of upper mantle — just beneath the lithosphere

What Type of Plate Boundary Is the San Andreas Fault System On?

Transform boundary

What type of plate boundary is found between the North American plate and the Juan de Fuca plate?

Convergent boundary

Why do volcanoes happen at subduction zones?

Post collision, the sinking, denser, tectonic plate releases water into the hot mantle —> lowers the melting point of the rock to create magma that rises to the surface

Why do volcanoes happen at divergent boundaries?

Tectonic plates move away from each other and leave a gap — hot rock from mantle rises to fill space — heavy weight of crust is removed and causes a sudden drop in pressure — drops the melting point of the mantle rock and turns it into liquid magma that flows up through long cracks/fissures to form a new ocean floor/rift valleys on land

Pyroclastic Flows

Fast-moving, downslope transport of hot volcanic debris — rapidly buries areas near to volcanoes

Lava Flows

• Riverlike flows of lava; low viscosity melt

• Mostly mafic (magnesium + iron) composition

  • Divergent boundaries and/or hotspots

Poison Gasses

Gases dissolved in magma released at the surface

• CO₂ —> Can form pockets in low-lying areas when colder than surrounding air + causes asphyxiation in high concentrations

• SO₂ —> Irritant to eyes nose and throat

• H₂S —> Toxic in high concentrations + odor at low concentrations

• Hydrogen Halides (HF, HCl, HBr) —> Acidifies water

Acidic Water

CO₂, H₂S, HF, & HCl all contribute to acidity

• Acid rain

• Acid lakes

  • Tend to form in crater areas of volcanoes

  • pH can be as low as 0.1 during a time of high emission rates

  • Chemical burns to human skin

  • Unlikely to dissolve metal quickly

Volcanic Bombs

• Pyroclastic debris >64 mm (2.56 in) in diameter (can exceed 5 m)

• Often rounded or otherwise streamlined because of cooling in free fall

Ash Accumulation

• Fine (dust-sized) airborne particles —> rock fragments, melt cooled in free fall

• Explosive eruptions (high viscosity melt)

• Damaging effects —> major aviation hazard, water contamination, damage to buildings, vehicles, electrical systems, plant life

Lahars

• Mix of volcanic debris, water, and ice

• Akin to mudflows in behavior

Debris Flows

• Fast-moving landslide (can be >35 mph); caused either by intense rainfall or rapid snowmelt

• Can carry large objects (boulders, cars, etc.)

• Can travel several miles if they fall into a narrow channel

• Locations of recent forest fires are particularly susceptible

How do we monitor volcanoes?

• Monitor volcanoes with documented eruptions

• Look out for

  • earthquakes

  • ground movement (uplift/subsidence)

  • volcanic gas

  • changes in water chemistry

  • satellite analysis

• Indicators also include increases in activity or sudden changes

• Not 100% accurate — possible false alarms

Extinct Volcanoes

Ceased to erupt or show no signs of magmatic activity

Dormant Volcanoes

Hasn’t erupted recently but still shows potential to erupt + detected as ongoing magmatic activity

Active Volcanoes

Erupted in the Holocene epoch (past 11,650 years) or otherwise expected to erupt in the future due to underlying magmatic activity

Why Does Lightning Occur During Volcanic Eruptions?

Airborne volcanic ash particles collide —> builds up static electricity in ash plume —> discharge expressed as lightning — can be contributed to from moist air and airborne ice

What is the Recurrence Interval for Volcanoes?

Average length of time between an event of a given magnitude and an event of similar magnitude

Would an Acid Lake From a Volcano Corrode a Boat in a Matter of Minutes?

No, it would take much longer to corrode metals (the boat)

Ground Shaking

Falling buildings, liquefaction, and mass movements (landslides + rockfalls)

Liquefaction

Loosely packed, water-saturated soil temporarily loses its strength — behaves like a thick liquid during earthquake

Mass Movements

Downslope or downward movement of a solid, continuous (or discontinuous) mass, under influence of gravity

Tsunamis

Large, destructive, waves caused by a sudden large event —> can travel long distances

• earthquakes

• volcanic eruptions

• coastal landslides

Requires vertical motion underwater

The Richter Scale Being Logarithmic

Numerical value — taking log of wave amplitude —> every whole number value represents magnitude of 10x that of previous number

What is an Earthquake Swarm Event?

Series of earthquakes of similar magnitude in a local area in a short amount of time

Not the same as main shock (larger magnitude) followed by aftershocks (smaller magnitude)

Where Does Geothermal Heat Come From?

• Remnant heat (largest fraction)

• Frictional heat 

• Radioactive decay

Earth’s core + mantle

Where Does Earth’s Magnetic Field Come From?

Movement of liquid iron and nickel in outer core

How Does Earth’s Magnetic Field Relate to the Density of Earth’s Atmosphere?

Outer core circulates —> generates a magnetic field —> deflects charged particles from the sun

How Does Earth’s Magnetic Feld Relate to the Northern Lights?

Interaction between solar wind and upper atmosphere — only at poles cause of magnetosphere’s shape but can occur at lower latitudes of magnetic field is disrupted

How do Geodes Form?

Void spaces in rock:

gas bubbles in melt —> dissolution creates voids —> water enters void space —> dissolved minerals precipitate on void’s walls —> grow into mineral habit

Why is it Unlikely That There are Large Void Spaces in the Deep Subsurface?

The high pressure would make it collapse

What kinds of activities can cause human-induced earthquakes?

• Wastewater disposal (byproduct of oil production)

• Hydraulic fracturing (fracking)

• Nuclear detonations

Requires high rate and volume of injection + large faults to produce earthquake

Does Earth’s Magnetic Field Block Microwaves?

No, it does not

Why are There Volcanoes in Iceland?

Directly on plate boundary + decompression melting and hot spot

Why are There Volcanoes in Italy?

Ongoing collision —> due to subduction

How Does Oil Form?

From buried remains of tiny ancient marine organisms (algae, plankton, etc.)

How do diamonds form?

Crystalized carbon due to heat and pressure

How do diamonds get to the surface?

Magmatic activity and then eroded out of sources + mixed with other sediments