GLG 111 Study Guide - Midterm Guide: Hematite, Olivine, Magma Chamber
26 Jun 2018
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THE SCIENTIFIC METHOD
Scientific method: the general procedure for discovering how the universe works through
systematic observations and experiences
Qualitative data: data that deals with descriptions
Quantitative data: data that deals with numbers
Hypothesis: a tentative explanation based on data collected through observations and
experiments
Theory: a coherent set of hypotheses that explains some aspect of nature
Continental drift: large-scale movement of continents
Alfred Wegener: German meteorologist who wrote a book on the breakup and drift of
continents based on similarities in the geologic record on both sides of the Atlantic
How is an observation different from an interpretation? Give an example.
Observations are statements formulated by the results of an experiment that can be gathered
using any of the five senses: touch, taste, smell, hearing, or seeing. Interpretations are how
each person perceives these observations. For example, one can tell that a limestone rock
effervesces when it comes in contact with diluted HCl solution (observation) because of its
reaction with a mineral inside the rock (interpretation).
What are the three hypotheses for the formation of Meteor Crater? What are the strengths
and weaknesses of each hypothesis? Which hypothesis is currently the most favored?
Scientists believe that meteor crater was created by volcanic eruption, the collapse of a salt
dome, or a meteor impact. Currently, the leading hypothesis is meteor impact because small
fragments of a meteor have been found scattered outside the crater. No volcanic material or
salt was found around or below the crater.
Despite the overwhelming amount of evidence in support of his continental drift hypothesis,
Alfred Wegner was unable to convince geologists of his time to accept his hypothesis. Explain
the primary reason why this was the case.
Wegner could not explain why the continents are forced to drift or give a mechanism as to how
they drift. Later, it was discovered that mantle convection forces the plates apart or together,
causing area at plate boundaries to change as mantle is recycled.
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PLATE TECTONICS
Plate tectonics: explains the distribution of the world’s physiographic features, earthquakes
and volcanoes; the idea that continental or oceanic plates are always moving
Lithosphere: strong, rocky outer shell of the solid Earth that makes up the crust and upper
mantle that forms tectonic plates; approximate depth of 100 km
Asthenosphere: weak, ductile layer of mantle beneath the lithosphere that deform to
accommodate the vertical and horizontal movement of the plates
Divergent boundaries: plates move apart and new lithosphere is created, so the plate area
increases
Convergent boundaries: plates come together and one plate is recycled into the mantle, so the
overall area decreases
Transform boundaries: plates slide past each other, so plate area doesn’t change
Subduction zone: where one plate slides underneath another and is eventually recycled in the
asthenosphere
Spreading center: as the seafloor spreads, hot molten rock wells up into the rift created by a
mid-ocean ridge to form new oceanic crust
mid-ocean ridge: undersea mountain chain that exhibits earthquakes, volcanism and rifting, all
caused by the stretching forces of mantle convection
continental rift: divergent boundaries characterized by rift valleys, volcanism and earthquakes
distributed over a wider zone than at oceanic spreading center
convective drag: convective flow in the mantle “drags” the overlying plate along with it
slab pull: low density materials are driven out and minerals in the slab are pulled toward denser
material, so the subducted slab becomes denser than the mantle into which it is being
subducted, so the sinking slab “pulls” the plate into the trench
ridge push: newly created lithosphere at mid-ocean ridge is elevated relative to older-thicker
lithosphere towards trench, so the lithospheric plates slide “downhill”
hot spots: regions of intense, localized volcanism that can cause mantle plumes
List several lines of evidence that plates are moving?
Mantle convection leads to continental drift, which occurs because of convective drag, ridge
push or slab pull. Sea floor spreading leads to the creation of new lithospheric material, which
forces plates apart in one location and together in another, leading to the overall movement.
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find more resources at oneclass.com
How fast do plates move?
The rate at which plates move varies from plate to plate, but usually ranges from a few
millimeters per year to several feet per year.
New seafloor material is created everyday, why is the Earth not expanding?
When new seafloor material is created in one place, this causes the preexisting material
surrounding that area to be forced apart. This forces material in other places to come together,
leading to one plate being subducted under another, causing the process of mantle recycling to
begin.
Type of plate boundary Example
Divergent
1. Oceanic mid-Atlantic ridge
2. Continental East African rift valley
Convergent
1. Oceanic-oceanic Mariana islands
2. oceanic-continental Andes Mountains
3. continental-continental Appalachian mountains
Transform San-Andreas fault
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Scientific method: the general procedure for discovering how the universe works through systematic observations and experiences. Hypothesis: a tentative explanation based on data collected through observations and experiments. Theory: a coherent set of hypotheses that explains some aspect of nature. Alfred wegener: german meteorologist who wrote a book on the breakup and drift of continents based on similarities in the geologic record on both sides of the atlantic. Observations are statements formulated by the results of an experiment that can be gathered using any of the five senses: touch, taste, smell, hearing, or seeing. Interpretations are how each person perceives these observations. For example, one can tell that a limestone rock effervesces when it comes in contact with diluted hcl solution (observation) because of its reaction with a mineral inside the rock (interpretation). Scientists believe that meteor crater was created by volcanic eruption, the collapse of a salt dome, or a meteor impact.
