EPSC 201 Study Guide - Final Guide: Positron, Banded Iron Formation, Boiling Point
DepartmentEarth & Planetary Sciences
Course CodeEPSC 201
ProfessorAnthony Williams- Jones
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EPSC201 2006 Final Exam Review Section 5&6
1) Draw a structural cross-section through the Andes. Identify two types of faults on
the section and explain their origin.
Himalayas are continent-continent collision formed. The Rockies and Andes are the result of subduction
of an oceanic plate under a continental plate.
In extension environments, there is also mountain formation. Grabens and horsts are formed, and can be
up to a thousand meters high. There is a thinning of the continental crust when it is pulled apart, but there
is still ridge formation. The fault lines do not go straight downward in extension environments. They
seem to go down on an angle. The material responds to stretching differently depending on how ductile it
is. If very ductile, the continent will stretch and thin. However, if it is brittle, there will be fault formation.
2) Name and explain three criteria for establishing relative ages of rocks.
Uniformitarianism!is the assumption that the same natural laws and processes that operate in
the!universe!now, have always operated in the universe in the past and apply everywhere in the universe.
It has included the!concept that "the present is the key to the past" and is functioning at the same rates.
Uniformitarianism has been a key principle of geology and virtually all ﬁelds of science.
So this Danish bishop, Nicholas Steno, developed the principle of superposition. He proposed that the
top layer of rocks were the youngest, and the deepest rocks were the oldest. We now refer to this as
stratigraphy. This was his ﬁrst principle.
Steno’s second principle was that all sedimentary layers are formed in horizontal layers. He noticed
that canyons contained strata that traveled for long distances.
Steno’s third principle was the principle of original continuity. This states that if some amount of
sediment is worn away, you can pick up the same sediments some distance away, because at some time,
the sedimentary layer was continuous.
Based on cross cutting relationships, we know the vertical crosscut is the youngest.
Using fossil records can help with the determination of age. This can help us form a global age. Any
rocks with trilobites are about 400 million years old. Due to the progress of evolution, we see tiny
changes in fossil records, that can accurately determine the age of the rock. Looking at an outcrop with
fossils, and other rock layers, can help us determine rock layers a few thousand kilometers away, with the
exact same fossil records.
Fossils are good for relative ages, while radioactive dating is good for absolute aging. Combining these
two techniques makes it easy to date rocks.
3) What is an unconformity? Discuss the origin of two types of unconformity.
An!unconformity!is a buried!erosional!or non-depositional surface separating two!rock!masses or!strata!of
different ages, indicating that!sediment!deposition was not continuous.
Angular unconformity - An angular unconformity is an unconformity where horizontally parallel!strata!of
sedimentary rock are deposited on tilted and eroded layers, producing an angular discordance with the
overlying horizontal layers.
The ﬂat top layers have an angular relationship with the rocks layers below.
A!nonconformity!between sedimentary rocks and metamorphic or igneous rocks occurs when
sedimentary rock has been deposited above pre-existing (eroded) metamorphic or igneous rock,
indicating an environmental alteration in mode of formation of strata.
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