Don Barrie, Geoscience Educator

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Geology 100--General Geology

Exam No. 2 Study Guide

Know the factors that affect the eruptive style of a volcano. What is the basic textural difference between plutonic and volcanic rocks in terms of crystal size?  What are the different igneous rock textures and what do they tell us about the cooling histories of igneous rocks? 

Understand the differences between various volcanic landforms, including shield volcanoes, cinder cones, and stratovolcanoes.  Which type of volcano is most common at subduction zones?  Which type is most explosive?  Which types are associated with mafic magma?  Which type is associated with intermediate magma?  

Be able to distinguish between the two main types of weathering. List several examples each of mechanical and chemical weathering processes.  Be able to explain how susceptibility to chemical weathering relates to Bowen’s Reaction Series.  Be able to explain how mechanical and chemical weathering act together (i.e., reinforce each other) to disintegrate and decompose a rock mass.  Which type of weathering predominates in arid environments? In humid environments?  

Understand the principle of uniformitarianism and how this idea applies to the study of sedimentary rocks.

How are sedimentary rocks classified?  Be able to describe the common detrital, inorganic, and organic (biochemical) sedimentary rocks.  How does a detrital sediment change with transport distance in terms of rounding, sorting, and average grain size? 

Be able to describe at least two marine and two non-marine depositional environments.

What factors/agents contribute to the formation of metamorphic rocks?  How are metamorphic rocks classified? Understand the basic difference between regional, contact, hydrothermal, and dynamic metamorphism. Be able to distinguish different metamorphic textures, including slaty, phyllitic, schistose, and gneissic textures.  In which plate tectonic setting do most foliated metamorphic rocks form?  Be able to describe the textural characteristics of the following metamorphic rocks: slate, schist, phyllite, gneiss, marble, quartzite. 

Be able to draw out the rock cycle. 

How old is the Earth?  What is the difference between relative and absolute dating?  Be able to apply the principles of relative dating to reconstruct the sequence of geologic events in a region.

Know the time boundaries between the Cenozoic, Mesozoic, and Paleozoic Eras and between the Paleozoic Era and Precambrian time.  What types of fossils are dominant within each Era? 

Be able to explain the processes of radioactive decay, specifically alpha decay, beta decay, and electron capture. 

A hypothetical parent element has a half-life of 1,000,000 years.  If a radioactive mineral contains 25% parent and 75% daughter product, how old is the mineral (and thus the igneous rock containing the mineral?) 

Know the difference between an earthquake focus and epicenter.  Be able to describe the various types of seismic wave and the elastic deformation they cause.  Be able to distinguish between P waves, S waves, and Surface waves on a seismogram.  Understand the difference between seismic wave amplitude (wave height), seismic wave period (time between successive wave crests), and S-P time difference (time delay between first P waves and first S waves). 

     Selected Vocabulary



Detrital sedimentary rock

volcanic ash & tuff

Biochemical sedimentary rock


Inorganic sedimentary rock

shield volcano


stratovolcano (composite cone)


cinder cone


mechanical weathering


chemical weathering


Alpha/beta decay & electron capture

Grain size

Half life






Precambrian time


Paleozoic / Mesozoic / Cenozoic Eras

Ripple marks

Body waves (P-waves, S-waves)


Surface waves


Wave amplitude / period

Directed stress

S – P time difference

Non-directed stress




Slaty texture

Richter Scale

Phyllitic texture


Schistose texture


Gneissic texture


Regional metamorphism


Contact metamorphism


Hydrothermal metamorphism


Dynamic metamorphism


Relative dating


Numeric (absolute) dating