1. Geology – the study of the Earth and its processes
Earth Science Notes
Geology – the study of the Earth and its processes

2. The Earth’s Layers
Scientists study seismic (earthquake) waves and volcanic explosions to learn about the Earth’s interior.
Crust
Mantle
Outer Core
Inner Core

3. The Earth’s Layers cont…
Crust
outermost layer
thinnest layer
the layer we live on
divided into pieces, called tectonic plates
two types: continental and oceanic crust
Mantle
thickest layer
“flows” and allows the tectonic plates to move on top
primarily magma

4. Core is made primarily of iron and some nickel
The Earth’s Layers cont…
Outer Core
liquid
Inner Core
solid
dense, high pressure layer at the center of the earth
Core is made primarily of iron and some nickel

5. Alfred Wegener
proposed that all the continents were once joined as a single landmass
he called this “supercontinent” Pangaea
stated the continents have separated and collided as they have moved over millions of years
called his theory “continental drift”

6. Slide does not need to be copied
Continental Drift
Slide does not need to be copied 6

7. Wegener’s 5 major pieces of Evidence:
Continents (esp. South America & Africa) seem to fit together like pieces of a puzzle
Matching fossils occur on east coast of S. America & west coast of Africa
Matching folded mountain belts on coasts of S. America & Africa 7

8. Data for latitudes & longitudes of locations is changing
Evidence cont…
Evidence of ancient climates show landmasses were once located elsewhere
Ex: glaciers in Africa !
Data for latitudes & longitudes of locations is changing 8

9. Wegener is debated
Other scientists argued that the continents could not just plow through the oceans
Later evidence revealed Wegener was correct – he just didn’t have the technology to prove how the continents had moved

10. Modern Theory = Plate Tectonics
The crust is made up of about a dozen major, moving plates and several smaller plates
Plates can contain:
land = continental crust
ocean = oceanic crust
Both ! 10

11. Modern Evidence from the Oceans
Scientists mapping the ocean floor found:
Underwater mountain chains
Ridges where the sea floor was actually spreading at sites called ridges
Some oceans were growing wider from the middle
Fossils and other materials are moving apart on either side of ridges
Newer, younger crust was being created by magma at the ridges 11

12. Magnetic measurements of the crust
Modern Evidence cont…
Magnetic measurements of the crust
Polarity (magnetic north vs. south) changes every so many thousand years
Magnetic rocks on the ocean floor show reversals
Rocks are in equal bands on either side of the mid-ocean ridges

13. What Moves the Plates?
Convection currents are created as heated rock rises to the surface, cools, and sinks again.
These currents carry the plates as if they are on a
conveyor belt in
a process called
“slab pull.”

14. Convergent = where plates collide Divergent = where plates move apart
Two different plates meet at a boundary.
There are 3 types of plate boundaries:
Convergent = where plates collide
Divergent = where plates move apart
Transform = where plates move up against one another

15. Convergent Boundaries:
Type 1: continental / continental
When these 2 pieces of crust collide, they buckle and push upwards, forming mountains = uplift occurs
Ex: Himalayas & Mount Everest

16. continental crust continental crust Uplifted mountains
to draw & label:
Uplifted mountains
continental crust
continental crust

17. Type 2: continental / oceanic
Oceanic is denser, so it sinks at the trench between the plates = called the subduction zone
The melting of the oceanic crust forms new magma which is less dense than surrounding rock, so it rises, forming volcanoes
Ex: Mt. St. Helens 17

18. to draw & label: volcanoes continental oceanic trench crust crust
magma
melting
the mantle

19. Type 3: oceanic / oceanic
The denser plate is subducted / sinks.
The melting of the crust forms new magma which will rise above the denser rock – as it cools,
it may pile up to
form land
Ex: Hawaiian
Islands & Japan

20. to draw & label: land & volcanoes oceanic crust oceanic crust trench
magma
melting
the mantle

21. Hot Spots
In several places on earth, hot magma moves upwards through the crust
As a plate moves over this source of magma, volcanoes form at the hot spot.
As the plate
continues to move,
a chain of volcanoes
of differing ages
forms

22. Divergent Boundaries:
The area where 2 plates are moving away from one another is called a rift zone.
Magma will rise up to fill the gap, cool, and harden to form new crust.
When this happens in the ocean, the process is called sea-floor spreading.

23. Ex: Great Rift Valley in Africa – note: the inland sea that resulted
Ex: Mid-ocean ridge in the Atlantic – note: the youngest crust will be found in these areas
Ex: Great Rift Valley in Africa – note: the inland sea that resulted 23

24. to draw & label: oceanic crust oceanic crust mid-ocean ridge
sea-floor spreading
the mantle
magma

25. to draw & label: continental crust continental crust rift zone
subsidence
step 1
step 2
inland sea

26. Transform Boundaries:
Two plates may grind and jerk as they slide past one another.
The boundary where they meet is called a fault line.
The stressful movement often results in earthquakes.

27. Ex: San Andreas Fault
Transform Boundary
to draw & label:

28. continent Feature _____ is an ocean trench.
Feature _____ is undergoing subduction.
Feature _____ is part of the continental crust.
Feature _____ is part of the mantle.
Feature _____ is part of the oceanic crust.
continent
For discussion: C
ocean A B D

29. The “Ring of Fire”
- A large number of the world’s volcanoes and earthquakes occur around the edges of the Pacific plate