Geologic Changes Common Assessment Study Guide
The following topics will be included in the Common Assessment that will be given this Friday, February 13. This list
is to be used as a guide for working your way through the information in your binder. It does not include all things that
will be tested, and it should not be the sole study resource for the assessment. **As you review topics listed below, make
notes about the topics that are difficult for you. These are the things that you should spend a little extra time
reviewing/studying. **
Chapter 6 Plate Tectonics
--Lesson 1 Continental Drift Hypothesis (by Alfred Wegener)
 Pangaea (Proposed supercontinent)
 Evidence that Continents Move
o Climate Clues
o Fossil Clues
o Rock Clues
 What was missing? (couldn’t explain HOW continents moved & movement was too slow to measure)
--Lesson 2 Development of a Theory
 Mapping the Ocean Floor (mid-ocean ridges discovered)
 Seafloor Spreading
o Topography of the Seafloor (mid-ocean ridges, abyssal plain, trench, rift valley, subduction zone, etc)
o Moving Continents Around (interaction between oceanic & continental crusts at subduction zone)
 Development of a Theory
o Magnetic Reversals (normal polarity, magnetic reversals, reversed polarity)
o Rocks Reveal Magnetic Signature
 Explain how basalt gets permanent record of Earth’s magnetic field at time of eruption
 parallel patterns in basalt on each side of mid-ocean ridge
o Evidence to Support the Theory
 Parallel locations in each side of mid-ocean ridge match in 3 ways
 Describe thermal energy change in seafloor as distance from mid-ocean ridge increases
-Lesson 3 Theory of Plate Tectonics
 The Plate Tectonics Theory
o Tectonic Plates (a.k.a. lithospheric plates)
 Plate Boundaries
o Divergent Plate Boundaries (mid-ocean ridges, new seafloor & rift valleys)
o Transform Plate Boundaries (faults & earthquakes)
o Convergent Plate Boundaries (continental-continental, continental-oceanic, oceanic-oceanic, mountains,
subduction zones, trenches, volcanoes, earthquakes, etc)
 Evidence for Plate Tectonics (use of GPS for measurement & pattern of earthquake & volcano activity at plate
boundaries)
 Plate Motion
o Convection Currents in asthenosphere (magma moves due to differences in temperature & density)
o Forces Causing Plate Motion (basal drag, ridge push & slab pull)
 A Theory in Progress (unanswered questions)
Chapter 8 Earthquakes and Volcanoes
--Lesson 1 Earthquakes
 What are earthquakes?
 Where do earthquakes occur? (mostly in ocean near edges of continents)
o Earthquakes and Plate Boundaries (convergent, divergent & transform cause different strength quakes)
o Faults
o Earthquake Focus and Epicenter
 Seismic Waves (know what they are but don’t worry about the different types)
 Determining Earthquake Magnitude (recognize three ways of measuring magnitude)
--Lesson 2 Volcanoes
 What is a volcano?
 How do volcanoes form?
o Convergent Boundaries (at subduction zones of oceanic-oceanic and oceanic-continental)
o Divergent Boundaries (mid-ocean ridges)
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o Hot Spots (not near plate boundaries)
Where do volcanoes form?
o Ring of Fire
Types of Volcanoes (recognize that there are three types: shield, cinder cone & composite)
Effects of Volcanic Eruptions
o Lava Flows
o Ash Fall
o Mudflows
Chapter 9 Clues to Earth’s Past
--Lesson 1 Fossils
 Evidence of the Distant Past
o Catastrophism
o Uniformitarianism
 Formation of Fossils
o Conditions for Fossil Formation
 Types of Preservation
o Preserved Remains
o Carbon Films
o Mineral Replacement
o Molds
o Casts
o Trace Fossils
 Ancient Environments
o Shallow Seas
 Fossils of ancient sea organisms give clues about ancient seafloors that no longer exist
o Past Climates
 Fossils of plants and climate specific animals (ex. wooly mammoth) give clues about how climate
has changed
-Lesson 2 Relative-Age Dating
 Relative Ages of Rocks (Principles used to correlate rock samples from nearby locations)
o Superposition
o Original Horizontality
o Lateral Continuity
o Inclusions
o Cross-Cutting Relationships
 Unconformities
 Correlation
o Matching Rock Layers (according to relative age)
o Index Fossils (used to correlate rock samples from distant locations)
 3 requirements/criteria for a species to be an index fossil
 Be able to correlate layers using index fossils
 Be able to determine relative age of rock using index fossil
-Lesson 3 Absolute-Age Dating
 Absolute Ages of Rocks
 Atoms
o Isotopes
o Radioactive Decay
 Parent isotopes & daughter isotopes
o Half-Life
 Half-life graph
 Radiometric Ages
o Radiocarbon Dating (only useful for dating organic/once living material (living things contain carbon))
o Dating Rocks
 Igneous Rocks
 Sedimentary Rocks
o The Age of Earth
 Ages of rocks from Moon, meteorites & Earth compared to determine age of Earth