EARTHS PROCESSES EARTHS PROCESSES Africa & South America Fit - - PowerPoint PPT Presentation

EARTH’S PROCESSES

EARTH’S PROCESSES

• Africa & South America Fit

Video

• Super

Volcano As Seen From Montana Simulation

• Blast Zone Map
• Ash bed map from previous

Yellowstone eruptions

ALFRED WEGENER

• German scientist
• Noticed in the early 1900’s that some continents seemed to fit together as a puzzle
• Wegener hypothesized that these continents were once a great land mass or supercontinent

called Pangea

• 200 million years ago the super continent broke into pieces that drifted over the surface of the

Earth.

• He couldn’t explain how the pieces moved.
• Continents shared rocks, minerals, fossils

PANGEA

PLATE TECTONICS

• Earth’s plates are in constant, slow motion
• Between 2.5 and 15 cm per year!
• Since you’ve been alive, plates have moved more than 180 centimeters!!!
• Theory of plate tectonics states that Earth’s surface is made of pieces called plates and move over

the upper layers.

• T
• p of plate = continental or oceanic crust
• Bottom of plate = rigid layer of earth’s mantle
• T
• gether they make up the Lithosphere
• The process continues as the current earth/volcano hot spots of the world reflect the edges of the

moving plates atop which the continents sit.

PLATE TECTONICS

• Geologists came to the conclusion in the

1960’s that the Earth’s lithosphere was broken up into about 12 large pieces called plates that are moving relative to

• ne another.
• The lithosphere floats upon the

asthenosphere (upper mantle).

• Continental crust is less dense than
• ceanic crust.
• Continental crust is composed of granite.
• Oceanic crust is composed of basalt.

SEAFLOOR SPREADING

• Harry Hess uses sonar data to get maps
• f the seafloor.
• Found the MOR – mid Atlantic ridge
• Produced by sea floor spreading
• Magma forced upward because of its low

density

• Causes crust to crack and form twin

mountain ranges with a rift valley in between.

EVIDENCE OF SEAFLOOR SPREADING

• 1. Ages of sediments and rocks.
• Sediment near the continents are old at

the bottom and younger at top.

• Layers near the MOR are only of recent

age.

• Oldest rocks on continents are ~ 400

billion yrs.

• Seafloor rocks are , 200 million yrs.

EVIDENCE OF SEAFLOOR SPREADING

• 2. Magnetic Polarity of Rocks
• some rocks have iron
• When rocks form the iron minerals line

up along the current magnetic field.

• When rocks harden the magnetic
• rientation is “locked”
• Magnetic field reverses direction
• Seafloor shows rock bands with reversed

polarities

TYPES OF STRESS

• 3 Types of Stress: tension, compression and shearing.
• Tension: Pulls apart. Thins out crust.
• Compression: Pulls apart. Shortens

and thickens crust. Squeezes rock.

• Shearing: Rocks slip past each other.

TYPES OF PLATE BOUNDARIES

• Divergent Boundaries
• Convergent Boundaries
• Transform Plate Boundaries

DIVERGENT PLATE BOUNDARIES

• Tension stress
• 2 plates move apart
• Magma rises between, spreads out and

cools

• Forms new oceanic crust
• Exist as rift valleys

DIVERGENT PLATE BOUNDARY

• The Atlantic Ocean is getting larger as the

Western Hemisphere moves away from Europe and Asia while the Pacific Ocean is becoming smaller. This is occurring because the North and South American plates are moving westward.

• The Mid – Atlantic Ridge

DIVERGENT BOUNDARY

• A satellite view of the Sinai Peninsula

shows two arms of the Red Sea spreading ridge, exposed on land.

• This is the northern extension of Africa’s

Great Rift Valley.

CONVERGENT PLATE BOUNDARY

• Compression Stress
• Plates come together and collide
• Continental plate + oceanic plate
• Oceanic plate + oceanic plate
• Continental plate + continental plate
• Creates mountains, trenches, volcanoes,

earthquakes, tsunamis

SUBDUCTION ZONE

• A subduction zone is a convergent

boundary where two tectonic plates collide.

• Less dense thick continental plate moves

towards a denser, thin oceanic plate.

• Oceanic plate is forced down under the

continental plate.

• Volcanic arcs parallel these zones
• Has a deep sea trench that parallel too.

SUBDUCTION ZONES APPEAR AS DEEP OCEANIC TRENCHES. MOST OF THE CONTINENTAL MOUNTAIN BELTS OCCUR WHERE PLATES ARE PRESSING AGAINST ONE ANOTHER.

IN THE CROSS SECTION OF THE EARTH IN THE SOUTHERN HEMISPHERE, THE MAP SHOWS A SUBDUCTION ZONE THAT HAS CREATED THE PERU-CHILE TRENCH AT THE WESTERN EDGE OF SOUTH AMERICAN AND THE ANDES MOUNTAINS ALONG THE WEST COAST OF SOUTH AMERICA.

TRANSFORM PLATE BOUNDARIES

• Shearing stress
• When 2 plates slide past one another
• Horizontal motion
• Important when they cut perpendicular to

the MOR (mid ocean ridge)

SAN ANDREAS FAULT

• An aerial view shows probably the most

familiar meeting of two plates in the United States, the San Andreas fault slicing through the Carrizo Plain in the Temblor Range east of the city of San Luiz Obispo, CA.

VOLCANOES

• magma (melted rock inside Earth)rises to

the surface where the earth’s plates pull apart (divergent zones)

• “holes” in the plates called hotspots
• cooler oceanic crust dives underneath

continental crust (convergent boundary) forcing magma to rise to the surface

VOLCANOES

• Hotspots: active sites where large

amounts of magma move to the surface in a column like plume.

• Hotspots don’t move much, but the plates

above them do!

• Under oceanic plate = Hawaiian islands
• Under continental =

Yellowstone

EARTHQUAKES

• https://www.youtube.com/watch?v=_-

CNX9W_KPw

• Occur at the boundaries of Earth’s plates
• Occur at different depths depending on

the type of boundary

• Divergent = shallow, narrow zone
• Convergent = greater depth, wider zone

EARTHQUAKES

• Shaking of the Earth caused by massive

amounts of energy released when there is sudden movement at a plate boundary along a fault.

ELASTIC REBOUND THEORY

• An explanation for how energy is spread

during earthquakes.

• As rocks on opposite sides of a fault are

subjected to force and shift, they accumulate energy and slowly deform until their internal strength is exceeded.

• At that time, a sudden movement occurs

along the fault, releasing the accumulated energy, and the rocks snap back to their

• riginal undeformed shape.

ELASTIC REBOUND THEORY

• Focus:Where the earthquake starts

Epicenter: Place on Earth directly above the focus Locating Epicenters Video

SEISMIC WAVES

• Three types of waves
• -Primary Waves (P)
• -Secondary Waves (S)
• -Surface Waves

PRIMARY (P) WAVES

• Longitudinal waves that move faster then
• ther waves
• Compresses earth’s crust in front of it and

stretching the crust in back of it

• Alternately compress and expand the

material they pass through

• Can cause ground to buckle and fracture

SECONDARY (S) WAVES

• A transverse wave that moves more

slowly

• Cause materials to shake at right angles to

the direction of wave motion

• Cause ground to shake up and down and

sideways

SURFACE WAVES

• Moves only across earth’s surface
• Can move ground side to side and damage

foundations of buildings

• Another type moves like an elliptical. A

combination of up and down and back and forth motion.

• More destructive than P and S waves. Can

cause building to collapse because of their longer wavelength and rolling action

LOCATING EARTHQUAKES

• Earthquake Distance
• The epicenter is located using the difference

in the arrival times between P and S wave recordings, which are related to distance.

• Earthquake Direction
• Travel-time graphs from three or more

seismographs can be used to find the exact location of an earthquake epicenter.

• Measures ground motion. North and south,

east and west, up and down

LOCATING EARTHQUAKES

• Earthquake Distance
• The epicenter is located using the difference in the arrival times between P and S wave

recordings, which are related to distance.

• Earthquake Direction
• Travel-time graphs from three or more
• seismographs can be used to find the exact location of an earthquake epicenter.
• Earthquake Zones
• About 95 percent of the major earthquakes occur in a few narrow zones.

MEASURING EARTHQUAKES

MEASURING EARTHQUAKES

• Historically, scientists have used two different types of measurements to describe the size of an

earthquake

• —intensity and magnitude.
• Richter Scale – measures energy released at the focus
• Based on the amplitude of the largest seismic wave
• Each unit of Richter magnitude equates to roughly a 32-fold energy increase
• Does not estimate adequately the size of very large earthquakes

MEASURING EARTHQUAKES

• Momentum Magnitude
• Derived from the amount of displacement that occurs along the fault zone
• Moment magnitude is the most widely used measurement for earthquakes because it is the
• nly magnitude scale that estimates the energy released by earthquakes.
• Measures very large earthquakes

DESTRUCTION OF EARTHQUAKES

• 1. Seismic

Vibrations - Destroy buildings, bridges and roadway

• 2. Liquefaction-causes sinking

3. Tsunamis-wipe out coastal settlements

• 4. Landslides/mudslides-destroy settlements at lower elevations
• 5. Fire-due to electrical lines and gas lines

SEISMIC VIBRATIONS

• Damage from earthquake waves
• Damage to building depends on several

factors: a. Intensity and duration of vibration b. Nature of the material on which the structure is built c. Design of the structure

LIQUEFACTION

• A process by which water-saturated sediment

temporarily loses strength and acts as a fluid.

• This effect can be caused by earthquake shaking
• Earthquake waves cause water pressures to

increase in the sediment and the sand grains to lose contact with each other, leading the sediment to lose strength and behave like a liquid. The soil can loose its ability to support structures, flow down even very gentle slopes, and erupt to the ground surface to form sand boils

TSUNAMIS

• A tsunami triggered by an earthquake
• ccurs where a slab of the ocean floor is

displaced vertically along a fault.

• A tsunami also can occur when the vibration
• f a quake sets an underwater landslide into

motion.

• Tsunami is the Japanese word for “seismic sea

wave.”

• When the ocean floor at a plate boundary

rises or falls suddenly, it displaces the water above it and launches the rolling waves that will become a tsunami

LANDSLIDES/MUDSLIDES

• Frequently triggered by strong ground

motions

• earthquakes create stresses that make

weak slopes fail

• earthquakes of magnitude 4.0 and greater

have been known to trigger landslides

• If the ground is saturated with water,

particularly following heavy rainfall, the shaking will result in more landslides than normal.

FIRES

LAW OF STRATIGRAPHY

• Created by Nicolaus Steno 17th century

Danish geologist

• Describe the patterns in which rock layers

are deposited.

• There are 4 laws:

1. Law of superposition 2. Law of original horizontality 3. Law of cross cutting relationships 4. Law of lateral continuity

LAW OF SUPERPOSITION

• Younger layers of rock sit atop older

layers.

LAW OF ORIGINAL HORIZONTALITY

• Layers of sedimentary rock are originally

deposited flat because of gravity.

• Any rock layers that are now folded and
• r tilted are by later outside forces.

LAW OF CROSS CUTTING RELATIONSHIPS

• Sometimes magma pushes, or intrudes,

into cracks in existing rocks. When the melted rock cools and solidifies, the resulting feature is called an igneous intrusion.

• An igneous intrusion is always younger

than the rock it cuts across.

LAW OF LATERAL CONTINUITY

• Layers of sediment initially extend laterally

in all directions.

• Rocks that are otherwise similar, but are

now separated by a valley or other erosional feature, can be assumed to be

• riginally continuous.

RADIOACTIVE DATING

• The nuclei of some isotopes decay, emitting energy at a fairly constant rate – radioactive
• The radioactive elements that make up minerals in rocks decay over billions of years.
• The rate at which they decay can help determine the age of the rocks
• Measures the amount of original radioactive material left undecayed in the rock and the

product of the radioactive materials decay.

• The amount of time that has passed since the rock formed can be calculated from this ratio.

HALF - LIFE

• The time in which half a radioactive

substance decays.

• Can measure how quickly a substance can

decay

• Example: potassium – 40 decays into argon

– 40. so the ration of potassium – 40 to argon – 40 is smaller for older rocks.

EARTH’S TIMELINE

• Planetary Accretion
• Planetary Cooling
• Core Formation
• Formation of Moon
• End of Heavy Bombardment

EARTH’S TIMELINE

PLANETARY ACCRETION

• The accumulation of particles into a

massive object by using gravity to attract more matter, typically gaseous matter, in an accretion disk.

• Small particles collide and stick together

to form larger masses

• Galaxies, stars, and planets, are formed by

accretion processes.

PLANETARY COOLING

• A planetary body, whether the body is a

planet or a moon, has to cool off. The warmth contained inside a body controls what sort of surface activity, atmospheric activity, and interior activity which the body has.

• As planetary bodies cool slowly, heat

diminishes, and the activities diminish to nothing

EARTH’S TIMELINE

CORE FORMATION

• When Earth was formed about 4.5 billion years

ago, it was a uniform ball of hot rock. Radioactive decay and leftover heat from planetary formation (the collision, accretion, and compression of space rocks) caused the ball to get even hotter.

• Eventually, after about 500 million years, our

young planet’s temperature heated to the melting point of iron.

• Relatively buoyant material, such as silicates,

water, and even air, stayed close to the planet’s exterior.

FORMATION OF MOON

• Giant Impact Hypothesis: moon formed when

an object smashed into early Earth.

• Co Formation

Theory: moons can also form at the same time as their parent planet. Under such an explanation, gravity would have caused material in the early solar system to draw together at the same time as gravity bound particles together to form Earth.

• Under the capture theory, a rocky body

formed elsewhere in the solar system could have been drawn into orbit around Earth.

EARTH’S TIMELINE

End of Heavy Bombardment

• About 4 to 3.8 billion years ago a period
• f intense comet and asteroid

bombardment is thought to have peppered all the planets including the Earth.

• Many of the numerous craters found on

the Moon and other bodies in the Solar System record this event.

CONVECTION CURRENTS

• Transfer of energy by the movement of

fluids with different temps. Convection Current: 1. Bottom of fluid is heated 2. Particles move faster, forces decrease and spread apart 3. Become less dense 4. Particles rise and cooler more dense particles sink

DENSITY AND BUOYANCY

• Density: the mass per unit volume of a

substance.

• Density = mass/volume
• Buoyancy: the force with which a more

dense fluid pushes a less dense substance upward.

WEATHERING AND EROSION

• Weathering: process that breaks down rocks and other substances at Earth’s surface.
• Erosion: movement of rock particles by wind, water, ice and gravity.
• 2 Types of weathering: mechanical

chemical

MECHANICAL WEATHERING

• Rock is physically broken into smaller

pieces.

• Freezing, thawing, release of pressure,

growth of plants, animal actions, and abrasion

• Abrasion: grinding away of rock by rock

particles carried by water, ice, wind, or gravity.

MECHANICAL WEATHERING

• Works slowly
• A physical change – change in size, shape,

phase etc..

• Does not alter the substance.
• Ice Wedging: wedges of ice in rocks

widen and deepen cracks. Ice melts, water seeps deeper. Repeated freezing and thawing and the cracks expand over time until pieces of rock break off.

CHEMICAL WEATHERING

• Process that breaks down rock through

chemical changes.

• Chemical change: changes from chemical

reactions in which a substance changes into another substance.

• Agents: water, oxygen, carbon dioxide, acid

rain, living organisms

• Produces rock particles that have a

different chemical makeup

CHEMICAL WEATHERING

• Water: dissolves rocks
• O2: combines with Fe and oxidizes
• CO2: dissolves in rainwater to make

carbonic acid. Effects granite and limestone

• Living organisms: plant roots produce a

weak acid.

• Acid rain: Acid speeds up weathering

process

RATE OF WEATHERING

• Most important factors: type of rock

climate – temperature and precipitation surface are

• Rocks: depends on minerals. Permeable rocks weather easily. Water goes through spaces and

removes dissolved material by weathering.

• Climate: average weather conditions

wet climate = fast reactions high temperatures = fast reactions