Dynamics of the Earth
May 18, 2015
Dynamics of the Earth
I. Evidence of Crustal Motions:
A. ________________ wears down the earth’s crust.____________ _______________ creates new mountains.
Weathering & Erosion
( Uplift )Plate tectonics
B. Sedimentary beds are
deposited as_______________
__(_____ _)
Horizontal Layers
Strata
THIS SEDIMENTARY STRATA SHOWS NO EVIDENCE OF UPLIFT OR CRUSTAL MOTION LAW OF
ORIGINAL HORIZONTALITY
C. Evidence of motions within
the Earth’s crust is indicated by:1._____________2._____________3._____________
TiltingFoldingFaulting
TILTING
FOLDING
FAULTING: OFF SET LAYERS
FAULTING
D. ______________provide direct
evidence of crustal movement.
Earthquakes
World Distribution
U.S . Distribution
_______ ______ and________ _______
are 2 changes thatcan be observed after
an earthquake.
Fault lines Uplifted land (displaced strata)
EARTHQUAKE DAMAGE
E. ______ ________are used in mapping surveys and indicate exact positions and
elevations.
Bench marks
Changes in ________________
of benchmarks are evidence that the
land is either ___________
or____________risingsinking
elevation
F.Displaced marine fossils found in mountains have 2
interpretations:
1. ____________________________________________________________
2. _____________________________________________________________
Higher sea levels covered mountains
Rocks were upliftedfrom a previous ocean bottom
G. _____________is the rising of the crust_____________
is the sinking of the crust
Uplift
Subsidence
II: EARTHQUAKES
1. The movement of ____________ inside
_______________
2. _______________ is the movement of rock along a surface where the rocks are broken.
A. 2 processes that cause earthquakes:
magma
volcanoes
faulting
B. ________ movement of the crust over long periods of time builds ___________
within the rocks.
Slow
stress
Increased pressure causes the _______ _______
to break creating a ________.
Rock strata
fault
When faulting occurs energy radiates through the earth as ________ ________ that cause the ground to_______________
Seismic waves
vibrate
III.Measuring the Earthquakes:
A. There are 2 scales to measure earthquakes:
1. ________________
2. ________________
Mercalli
Richter
B. _______________ scale is based upon the observations of people and damage caused. It
measures ___________ of the earthquake from____ to ____
Mercalli
intensity
1 12
Mercalli Scale – Intensity scale
I
II
III
IV
V
VI
C._______________
uses the seismograph to determine the ________________
Magnitude is the total______ released by the earthquake.
Richter Scale
magnitude
energy
Its numerical scale is ____ to ____.
Each of the numerical steps represent ____ increase.
1 10
31X
Richter Scale – Magnitude scale
V. Parts of the Earthquake:
A. The place underground where the break or fault occurs is the _______ of the quake.
focus
The __________ is the location along the surface of the earth just above the focus where the earthquake is felt most strongly.
epicenter
A. The 2 most important energy waves are:
P-wave or Primaryand
S-wave or Secondary
P-wave
Primary Wave
S-wave
Secondary wave
B. Characteristics of Primary Waves (P)
waves: _______________________ _______________________
_______________________ _______________________
Faster than S wavesRecorded first
travels through both solids and fluids
C. Characteristics of Secondary Waves (S)
waves: _______________________ _______________________
_______________________
_______________________
Slower than P wavesRecorded after P-wave
Can not travel
through fluids
TYPES OF EARTHQUAKE WAVES
D. Both S and P
waves travel faster through ___________
material.denser
VI. Finding the Epicenter:
A. The seismograph records the ________________ and
________________________________________
magnitude
Records arrival time of seismic waves
Use reference table page 11
Seismograph
B. The steps for calculating your distance from the
epicenter:
1. ________________________2. ________________________
3. ________________________
4. ________________________
Subtract arrival time of P from arrival time of S
Mark the interval on Y-axis
Slide marks to match P & S curve
Follow down to x-axisand read distance
01:10:00 01:20:0001:18:00 01:24:00
Step 1 Subtract the arrival time
of the P wave from the
arrival time of the S wave
01:24:00 - 01:18:00 00:06:00Lag time= 6 minutes !!!
Step 2
Mark the interval on the Y-axis
Step 3Slide the marks to
match the P and S Curves.Make sure the
paper is straight!
Step 4Follow down to the X-axis
and read distance
Practice questions:
1. The arrival of the P-wave is 12:03:00.
The arrival of an S-wave is 12:07:00 the difference is:
How far is this earthquake from the seismic station? 4 minutes
2600 Km
Practice questions:2. The arrival time of the
P-wave is 2:05:00The arrival of the S-wave is 2:08:00
the difference is:How far is this earthquake from the seismic station?
3 minutes
1800 Km
Practice questions:
3. If the difference in arrival time between P and S waves is 2 minutes 35 secondswhat is the distance from the earthquake to the
Seismograph stations?1500 Km
Practice questions:
4. How long does it take for a P-wave to travel from the focus of an earthquake to a seismograph station 2,000 km. away?
4 minutes
Practice questions:5. What is the difference in
arrival time between P and S waves for an earthquake
that is 5,000 kilometer away from a seismograph station?
6 mins 40 secs
VII. THE ORIGIN TIME OF AN EARTHQUAKE:
A. Earthquake waves detected at _______ times by observers are at _______ distances from the epicenter.
later
greater
B. To find the origin time seismologists need to
know:1. _____________________
2. _____________________
Arrival time of P-wave
Travel time of P-wave(how long it took)
Example:
A seismograph recording station located 5,700 km. from an epicenter.
It receives a P-wave at 2:45pmAt what time did the earthquake actually occur at the epicenter?
First:use the distance to find outthe travel time.Then: subtract the travel time from the arrival time.
The answer is:
9 min.
2:36
SF = San Francisco 300 km
LV = Las Vegas 390 km
LA = Los Angeles 189 km
Seismic Stations
TRIANGULATION TO FIND THE EPICENTER
SF
LVLA
300 km
VIII. THE LAYERS OF THE EARTH:
A. The crusts thickness______ It is _________________ under the oceans and
_________ under continents.
varies
thinner
thicker
Continental crust is mostly_______________, ____________density & __________________
The ocean basins are mostly ________ and ______ or ___________
granitic
dark densebasaltic
lowlight
B. Inferred characteristics of Earth’s
Interior:1. Studying the _____________
of _____________ ________ allows us to make inferences about the structure and composition of the Earth’s interior.
transmission
EarthQuake Waves
S-waves can not pass through liquid
P-waves are bent as they passthrough the different layers
Based on the density of the layer
2. The _____________ of a seismic wave changes with the __________ of the material it travels through.
Waves are also ___________ (bent) as they travel through different densities
velocity
density
refracted
We know that P-waves can be transmitted through
________ _______ & ______
S-Waves can be transmitted through ONLY
________________
solid liquid gas
solid
3. Earth Quake Shadow Zones:When an earthquake occurs both
____________ are received from most of the earth.
Opposite sides of the earth where the epicenter is, receives
____ but NO _______ because S-waves can not penetrate the _______ outer core.
S and P waves
SP
liquid
S-waves can not pass through liquid
____________ occurs at the ___________ (boundaries)
refraction interfaces
Let’s Draw This Diagram in our Notebook: