ANSWERS Introduction to Physical Geology
“Geology is the science that studies Earth -- how it was born, how it evolved, how it
works, and how we can help preserve it.”
Physical Geology is the division of geology concerned with earth materials, changes in
the surface and interior of the earth, and the dynamic forces that cause those changes.
How does Geology effect us??
Avoiding Geologic Hazards
1. Don’t build buildings in or around earthquake zones
2. Don’t build buildings in or around volcano zones
3. Don’t build buildings in or around mudslide prone areas
4. Build buildings up to the security codes needed for that region
5. Don’t build buildings to close to the shore, coast or other erosion prone areas
Supplying things we need
1. Energy
2. Oil
3. Food
4. Minerals
5. Metals
6. Space
7. Oxygen
8. Water
Protecting the environment
1. Prevention by understanding
2. Mining carefully
3. Renewable energy
4. Water conservation
5. Preventing contamination of water etc
Understanding our surroundings
1. Understanding the physical and biological world (nature)
2. Understanding the geological structures
Important Physical Geology Concepts
The earth is a giant machine driven by two engines: External and Internal
Earth's internal heat engine is:
 Produced by heat moving from the hot interior of the earth toward the cooler
exterior, this can produce moving plates, earthquakes and volcanoes.
Earth's external heat engine is:
 Driven by solar power
INTERNAL ENGINE
The Earth’s Internal Heat Engine –
 Hot buoyant material (MAGMA) deep
within the earth moves slowly upward
toward the cool surface (CRUST). As it
cools at the crust it sinks back down towards
the core.
Earth’s Interior - There are three zones:
Mantle – The largest zone of the earth. It is solid rock but it flows slowly. This layer
separates the crust (above) from the core (below).
Crust – The thin outer layer of the earth.
Two parts, continental (where we live) and oceanic (the bottom of the ocean).
Core – The center.
Inner core made of Iron & nickel. Outer core - the rotation of the outer core creates the
magnetic field.
Lithosphere: The rigid outer shell opf the earth. 70-125 km thick.
The upper mantle, made of solid rock. The lithosphere makes up the tectonic plates.
“Litho” means rock.
Asthenosphere: The lower mantle, made of a lubricating material on which the
lithosphere moves. “Asthenos” means weak.
Tectonic Forces: The forces generated by the inside of the Earth – (the internal
engine). The forces that result in uplift, movement or generate deformation in rocks of
the crust, (earthquakes, volcanoes etc).
The Theory of Plate Tectonics
A theory is: A scientific concept that has been highly tested and in all likelihood is true.
A hypothesis is: a tentative answer to a question, or solution to a problem.
Continental drift hypothesis: The hypothesis of continental drift was proposed in
1960’s and has resulted in the theory of Plate tectonics.
Plate tectonics: Plate tectonics regards the lithosphere as
broken into large plates that are in motion. The plates, which
are like segments move around on the asthnosphere
Mid oceanic ridges:A giant trange that lies underneath the ocean and extends around
the world.
Magma: Molten rock, usually mostly silica. The liquid may contain dissolved gases as
well as some solid material.
Subduction zone – Elongated region in which subduction takes place
Oceanic trenches – A narrow deep through parallel to the edge of a continent or an
island arc
Extrusive igneous rock – Any igneous rock that forms at Earths surface, whtehr it
solidifies directly from lava flow or is pyroclastic
Intrusive igneous rock – rock that has appared to have crystallized from magma
emplaced in surrounding rock.
Metamorpic rock – a rock produced by metamorphism
* Metamorphism – The transformation of the preexisting rock into texturally or
mineralogically distinct new rock as a result of high temperature, high pressure, or both.
This occurs without the rock melting int eh process.
There are three types of plate boundaries:
1. Divergent boundaries – Exist where plates are moving apart
2. Transform boundaries – Exist where tow plates are sliding past each
other
3. Convergent boundaries - Exist where plates are moving toward each
other.
EXTERNAL ENGINE
The Earth’s External Heat Engine:
Isostatic adjustment
Erosion
Equilibrium
Sediment
lithified
Sedimentary rock