Transcript Geology * Part II - Hatboro

Geology – Part II
Earth’s Interior, Plate Tectonics,
Earthquakes, Volcanoes & Earth’s
History
Earth’s Interior
1.Earth’s interior is divided into the:
a. Crust
b. Mantle
c. Outer core
d. Inner core
surface
center of earth
2. The lithosphere includes the crust and the
rigid upper layer of the mantle.
3. The Asthenosphere lies below the lithosphere
and is made up of the soft layer of the mantle.
Earth’s Interior
Plate Tectonics
1. Plate – lithosphere is broken into separate
sections called plates
2. Alfred Wegener developed the idea that the
continents were once joined and have since
drifted apart. The once giant land mass was
known as Pangaea.
3. The Theory of Plate Tectonics explains the
plate constant, slow motion, driven by
convection currents in the mantle. It
combines the theories of continental drift and
sea-floor spreading.
Plate Tectonics
a. Plates move in the following ways:
i. Transform Boundaries - slip past one another/No
change in elevation (stress = shearing)
ii. Divergent Boundaries - move apart/may cause a
change in elevation (stress = tension)
iii. Convergent Boundaries - come together/may cause a
change in elevation (stress = compression)
Plate Tectonics/Plate Boundaries
Diverging Plate Boundary
Converging Plate Boundary
Transform Plate Boundary
Earthquakes
A. Description
1. An earthquake is the shaking and
trembling that results from the movement of
rock beneath Earth’s surface
2. Earthquakes occur because of stress built
up in rock. Stress is a force that acts on a rock
to change its shape or volume. These stresses
cause faults (a break or crack in Earth’s
lithosphere (underground) along which the
rocks move). There are three types:
a. Shearing – Strike-slip Fault
b. Tension – Normal Fault
c. Compression – Reverse Fault
Plate Tectonics & Faults
Tension
Normal Fault
Compression
Earthquakes
B. Measuring Earthquakes
1. Seismic Waves – vibrations that travel through
Earth carrying the energy released by an earthquake.
a.
Primary Waves – P waves arrive first
move by compression and expansion
b.
Secondary Waves – S waves arrive
second - move side to side and up and down
c.
Surface Waves – when P and S waves
meet the surface – move in different
directions
2. Epicenter – center of the earthquake ON Earth’s
surface; in order to find the epicenter of an
earthquake, you need data from 3 cities
Earthquakes
C. Earthquake Hazards
1. Soil Conditions/Shaking
2. Liquefaction – violent shakes turn loose, soft soil into mud
3. Aftershock – earthquake that occurs after a big earthquake in the same
area
4. Tsunamis – large wave caused by an earthquake on the ocean floor
D. Earthquake Safety
1.
2.
3.
Location – some places are more prone to earthquakes
Construction – earthquake-proof buildings/houses (base-isolated buildings)
Drop, cover and hold
E. Earthquake Detecting Devices – 4 fault monitoring devices
1. Creep Meters – uses a wire across a fault to measure horizontal
movement of the ground
2. Laser-ranging Devices – uses a laser to measure horizontal movement
3. Tiltmeters – measures tilting or raising of the ground
4. Satellite Monitors – uses GPS from outer space to monitor changes in
elevation as well as horizontal movement along a fault
5. Seismographs – collects data (seismic waves) from earthquakes
Volcanoes
A. Description
1. A volcano is an opening in Earth’s Surface
where magma escapes from the interior.
Magma is the liquid inside a volcano. When
magma reaches earth’s surface it is called
lava.
2. Most volcanoes occur near the boundaries
of Earth’s Plates and along the edges of
continents above subduction zones, in island
arcs, or along mid-ocean ridges (under water
mountain ranges)
Earthquakes & Volcanoes
Volcanoes
B.Volcanic Landforms
1. Shield Volcanoes – Hawaiian Islands; quiet
eruptions, lava flows, wide base, not very tall
2. Cinder Cone Volcanoes – Paricutin in Mexico;
explosive eruptions of cinders/rock/gases – tall,
narrow base
3.Composite (Strato) Volcanoes – alternating
quiet/explosive eruptions – alternating layers of
lava and ash; Mt. Hood, Mt. St. Helen’s, Mt.
Ranier
Volcanoes
C. Volcano hazards
1.Pyroclastic flows
2.Damage from ash
3.Lava Flows
4.Avalanches of mud
5.Flooding
6.Deadly gases
Volcanoes
D.Volcano Benefits
1. Fertile Soil
2. Increased Tourism
3. Energy source
Historical Geology
A. Measuring Time
1. Relative Time (Relative Age) –
Measurement of time using comparison. No
numbers used; uses words like younger and
older.
a. Example – Joe is older than Mike
2. Absolute Time (Absolute Age) –
Measurement of time using actual numbers
a. Example – Mike is 15 years old
Historical Geology continued
B. Measuring Earth’s Age (Relative Time)
1. Many Paleontologists use rock layers
a. Fossils are mainly found in sedimentary
rock.
b. The layers help tell the relative age of
rocks
c. The LAW OF SUPERPOSITION states that
oldest layers of rock are on the bottom and
younger layers are on the top.
Historical Geology continued
• Unconformity – eroded rock surface pushed up
from deeper within earth that is much older than
the new rock layers above it.
• Glacial Till – large buildup of rock pieces carried
away in the bottom of a glacier
• Kettle Lake – lake formed when a large block of
glacial ice melts leaving a depression in the
ground.
• Drumlins – long, smooth, canoe shaped hills made
of glacial till
• Peat – substance made of decayed plant fibers,
softest type of coal
Historical Geology continued
2. Faults can be used to help determine the
relative age of a rock layers and the order in
which events happened.
a. A rock layer had to occur before a fault can occur.
b. Younger features cut across older features – this is
called CROSSCUTTING RELATIONSHIPS
3. A fault is a break or crack in part of Earth’s crust.
4. UNCONFORMITY – a break in the rock record that
separates series or layers of deposits.
a. Layers that are exposed above sea level are often
times eroded away with brand new layers being
deposited above the erosion mark.
Historical Geology continued
C. Determining Absolute Age
1. Radioactive Dating
a. The breaking down of atoms to form
different isotopes of the same element or a
completely new element
Carbon-14
Carbon-12
b. Energy is given off in the form of
- Gamma Rays
- Alpha Particles
- Beta Particles
Historical Geology continued
2. Half-Life
a. The amount of time it takes for half of the
original atom to decay
1. Uranium-238 = 4.5 billion years
2. Carbon-14 = 5,700 years
3. Oxygen = 19 seconds
b. In the amount of time give (half-life time),
half of the original substance will be gone.
Historical Geology continued
c. Example: If we start with 20 grams of carbon14, how long will it take to break down to 5
grams
Start of 0 years
5700 years
11, 400 years
=
=
=
20 grams
10 grams
5 grams
As you move down the left hand side of these
equations, keep ADDING THE HALF-LIFE
AMOUNT. As you move down the right hand
side of these equations, divide by 2 (take
half!)
Historical Geology continued
Fossils
A. Description - Any remains or evidence of a
living thing
B. Types
1.
2.
3.
4.
5.
6.
Shells
Bones
Pollen/Grains
Seeds
Imprints
Molds & Casts
Historical Geology continued
C. Formation of Fossils
1. Preservation without change
a. Frozen plants or animals/objects
stuck in amber (pine tree sap/resin) or
tar
2. Replacement by a mineral
a. Material decays and is slowly
replaced by a silicate (petrified wood)
Historical Geology continued
3. Formation of a carbon film
a. As material decays a carbon film is left
behind
1. Used only with living things
2. Used with half-life
4. Formation of an imprint – mold
5. Filling of an imprint – cast
D. Index Fossils – special marker used by geologists
to identify layers of rock that are separated far apart.
Geologic Time
A. Divisions
1. Eras – largest division of geologic time
a. Pre-Cambrian
*** can be broken down into eons***
b. Paleozoic
c. Mesozoic
d. Cenozoic
Geologic Time
2. Periods – subdivision of an era
a. Paleozoic Era – age of the invertebrates
1. Cambrian Period
2. Ordovician Period
3. Silurian Period
4. Devonian Period
5. Carboniferous Period – broken down into
Pennsylvanian & Mississippian in North
American only
6. Permian Period - ** The trilobite died out at
the end of the Permian Period, marking the end
of the Paleozoic Era
Geologic Time
b. Mesozoic Era – age of the reptiles/dinosaurs
a. Triassic Period
b. Jurassic Period
c. Cretaceous Period
** The dinosaurs died out at the end of the
Cretaceous Period, marking the end of the
Mesozoic Era
Geologic Time
c. Cenozoic Era – age of the mammals
1. Tertiary Period
2. Quaternary Period
** Epoch – division of geologic time that occurs
only in the Cenozoic Era; breaks down
periods into smaller chunks of time
***CENOZOIC ERA, QUATERNARY PERIOD ARE
STILL GOING ON NOW!!!!