earth science 8 grade
TRANSCRIPT
Ms. Holton
Day 42
15 October 2019
EARTH SCIENCE
8TH GRADE
WELCOME!
YOUR BELL WORK FOR TODAY IS…
❖ Read “Breakup” article
❖ Write a 2 – 3 sentence summary about the reading
HOMEWORK
❖ Unit 5 vocab (due next Friday)
❖ Read textbook pp. 122-132
❖ WB pp. 70-72
WHAT KINDS OF EVIDENCE DOES A GEOLOGIST USE
TO LEARN ABOUT THE EARTH’S INTERIOR?INSIDE THE EARTH
Direct evidence
Rock samples
Samples have been taken up to
12km in the crust
Forces can blast rock from up to
100km to earth’s surface
Indirect evidence
Seismic waves have speed and
direction
Using seismic wave data,
properties of different layers can
be inferred
EARTH’S LAYERS
EACH LAYER VARIES GREATLY IN TEMPERATURE , PRESSURE, SIZE & COMPOSITION
Temperature
Cool at surface to ~20 m
Increases 1°C for every 40m for tens
of kilometers
Then, increases slowly but steadily
Causes: High pressure, radioactive
substances, leftover thermal energy
from planet formation
Pressure
P = F/A
What creating the force?
More weight above = more pressure
below
THE CRUST
SOLID ROCK
Includes dry land & sea floor
“Like an onion skin”
Surface layer much thinner than
below layers
Averages 5-40 km in most places
Thickest under high mountains
Up to70 km
Continental crust is rocks like granite
Thinnest under ocean
< 5 km
Crust beneath ocean is mostly basalt
THE CORE
TWO PARTS. MOSTLY IRON & NICKEL.
Outer Core
Molten metal surrounding inner core
Liquid & in movement
Inner core
Dense ball of solid metal
Extreme pressure squeezes the
atoms of iron & nickel so much they
can’t become liquid
Core may contain other
substances
Oxygen, sulfur, silicon
More research needed
Generates the Earth’s magnetic
field. MUCH is unknown. Why?
Ms. Holton
Day 43
16 October 2019
EARTH SCIENCE
8TH GRADE
WELCOME!
YOUR BELL WORK FOR TODAY IS…
❖ Rate Calculation worksheet
HOMEWORK
❖ Read 132 - 135
❖ WB pp. 73-75
❖ Unit 5 vocab (due next Friday)
THE WORLDS LARGEST MAGNET
Ms. Holton
18 October 2019
EARTH SCIENCE
8TH GRADE
WELCOME!
TODAY’S ACTIVITY IS…
❖ Read through Wegener’s Story and ANNOTATE the
reading.
❖ Work through Wegener’s Puzzling Continents
HOMEWORK
❖ Finish lab activity paragraphs
❖ Read pp. 136-140
❖ WB pp. 76-77
❖ Unit 5 vocab (due next Friday)
Ms. Holton
Day 43
21 October 2019
EARTH SCIENCE
8TH GRADE
WELCOME!
YOUR BELL WORK FOR TODAY IS…
❖ Mystery Box! Work with your partner, and choose a
mystery box.
❖ Before beginning, discuss what strategy you will use to
determine the structure of your box’s interior WITHOUT
OPENING THE BOX. Write your plan in the “Notes”
section of your observation sheet.
❖ Using your strategy, draw the interior of the box.
❖ Wait for further instruction…
Carefully open your box (save the tape!) and
see how you did. Discuss how well your
strategy did (or did not) work.
How might you adjust your strategy next time?
HOMEWORK
Wegener’s Puzzle Paragraphs (due tomorrow)
Unit 5 vocab (due Friday)
INFERRING ABOUT THE CORE FROM EARTHQUAKES
THE FOCUS OF AN EARTHQUAKE (F)
GENERATES TWO TYPES OF SEISMIC
BODY WAVES:
“Compressional” waves,
called P-waves (in red)
Can travel everywhere within the
Earth, but in different ways
depending on the medium
“Shear” waves, called S-
waves (in purple)
Are slower and cannot travel
through liquids.
© C. Hein for the CNRS Magazine
F
Ms. Holton
22 October 2019
Period 4 & 5
EARTH SCIENCE
8TH GRADE
WELCOME!
TODAY’S ACTIVITY IS…
❖ Complete the Seismic Wave Worksheet
HOMEWORK
❖ Read pp. 141 – 147
❖ WB pp. 79 – 80
❖ Unit 5 vocab (due Friday)
THE MANTLE
HOT ROCK, BUT SOLID
Begins about 40 km below
surface
Three layers of the mantle
1. Lithosphere
Rigid
~100 km thick
2. Asthenosphere (upper mantle)
Hotter, higher pressure
Less rigid, but bends like plastic
Softer but still solid
3. Lower Mantle
Solid until the core
IF THE MANTLE IS SOLID/SEMISOLID, WHERE
DOES MOLTEN LAVA COME FROM?
THREE TYPES OF HEAT TRANSFER
THERMAL ENERGY ALWAYS MOVES FROM
WARMER TO COOLER SUBSTANCES
Radiation
Energy transfer by
electromagnetic waves
Conduction
Energy transfer by particle
collisions
Convection
Energy transfer by groups of
particles moving through fluids
Circular movement pattern
Density difference result in
convection
CONVECTION AND THE MANTLE
WELCOME!
TODAY’S ACTIVITY IS…
❖ Read the article about Marie Tharp
❖ Summarize (1) her key contributions and (2) how her maps changed the way scientists viewed the ocean floor.
HOMEWORK
❖ Read textbook pp. 150 – 154
❖ WB 81 – 83
❖ Unit 5 Vocab (due Friday)
❖ Reminder: Quiz on Monday
DRIFTING CONTINENTS
DO THE CONTINENTS MOVE?
Alfred Wegener (1910)
Hypothesized that all continents
were once a single landmass
Created the name “Pangea”
Drifted apart over time (“Continental
Drift”
Estimated 300 million years
Continental Drift hypothesis
Slow movement around Earth’s
surface
Wegener looked for other evidence
Land features, fossils, climate
change evidence
Turn to your partner and discuss the
theory of continental drift from a
SKEPTIC’s point of view.
Turn to your partner and discuss the
theory of continental drift from
Wegener’s point of view.
LANDFORM EVIDENCE – MOUNTAIN RANGES
Mountain belts line up on opposite sides of oceans.
FOSSIL EVIDENCE - MATCHING DINOSAUR FOSSILS
Same fossil organisms on separate landmasses
Separation usually produces differences in plants &
animals, even in the same species
mesosaurus
FOSSIL EVIDENCE – PLANT FOSSILS
CLIMATE EVIDENCE – GLACIERS
Assumes position of landmasses changed and that
Earth’s climate did not.
DRIFTING CONTINENTS – EVIDENCE SUMMARY
Land Features
Certain mountain ranges line up
(Africa & South America)
Certain coal fields line up (Europe &
North America)
Fossils
Glossopteris, a fern-like plant (Africa,
South America, Australia, India,
Antarctica)
Mesosaurus & Lystrosaurus reptiles
Found in places separated by oceans
Not believed to be able to swim
Climate
Tropical plants fossils found in polar
regions today
Glacier formations in South Africa
BREAKUP OF
PANGAEA
WELCOME!
TODAY’S ACTIVITY IS…
❖ “Getting Distance from Sonar” worksheet
HOMEWORK
❖ Hess, Matthew, and Vine reading with annotations
❖ Unit 5 Vocab (due Friday)
❖ Reminder: Quiz on Monday
A NEW THEORY EMERGES
Wegener’s hypothesis was rejected because it could
not provide explanation for why continents moved
In the 1960’s, sonar and deep-sea drilling provided
the explanation
Spawned new hypothesis: plate tectonics
SEA FLOOR SPREADINGCRUST IS ADDED TO SEA FLOOR FROM
THE MID OCEAN RIDGE
Mid Ocean Ridges
Discovered using sonar
Bounces sound waves off objects and
records their echo
The time for wave to return gives
distance to object
Like “seams” in crust
In all Earth’s oceans
Believe to be formed by sea-floor
spreading
Crust moves away like a conveyer belt
SONAR MAPPING
Maps ocean floor using sound waves to measure
distance of an object from the source of sound
Led to discover of a mid-ocean ridge across the
bottom of nearly every ocean
HAND PAINTED MAP OF THARP’S WORK BY BERANN
EVIDENCE GROWS FOR PLATE TECTONICS
“History of Ocean Basins”, 1962
Outlined idea of sea-floor spreading as an explanation for
continental drift
Harry Hess
“Magnetic anomalies over oceanic ridges”, 1963
Looked at magnetic stripes on the ocean floor, which align
with the magnetic field as new rock forms
Frederick Vine and Drummond Matthews
John Tuzo-Wilson
Hot spots form volcanic chains
Discovered transform faults (e.g., San Andreas)
J. TUZO WILSON (1960S) MOVEMENT OF HAWAIIAN
ISLANDS OVER A STATIONARY HOTSPOT
WHAT HAPPENS WHEN A RIDGE BREAKS THE
SURFACE? ICELAND!
WELCOME!
TODAY’S ACTIVITY IS…
❖ Tuzo-Wilson and McKenzie Reading
❖ Summarize how their contributions support plate
tectonics
HOMEWORK
❖ Rate of Plate Movement Worksheet
❖ Unit 6 Vocab (due Friday)
❖ Reminder: Quiz on Monday
Bring a calculator
on Monday!
EVIDENCE OF SEA FLOOR SPREADING
CRUST IS ADDED TO SEA FLOOR FROM
THE MID OCEAN RIDGE
…from Molten Material
1960s found rocks showing rapid
hardening of molten material
Many places along mid-ocean ridge
…from Magnetic Stripes
Patterns in rocks seem to indicate
magnetic pole reversal many times in
Earth’s history
“Stripes” show reversals in Earth’s
magnetic field
…from Drilling Samples
1968 a drilling ship gathered samples
Age estimates of rock seemed to show
older rock further away from ridges
FUTURE OF PLATE TECTONICS
REMINDER: CONVECTION AND THE MANTLE
Heat is transferred by convection
currents from the core and
mantle
Mantle rock flows VERY slowly
Convection in the mantle drags
the crust with it.
THEORY OF PLATE TECTONICS
EXPLAINS THE FORMATION, MOVEMENT
& SUBDUCTION OF EARTH’S PLATES
Plates
Lithosphere is broken into
sections
Plates fit together along cracks
Theory states:
Plates are in constant, slow
movement
Convection currents in mantle
drive movement
Movement causes major
changes in Earth’s surface
“Fault”
A break in the
crust where
rocks have
slipped past each
other
BOUNDARY TYPES
Plates move
apart
Plates come
together
Plates slide past
each other
CONVERGENT BOUNDARY EXAMPLES