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Geography 2122A/B Study Guide - Midterm Guide: Hydrosphere, Convergent Boundary, Geosphere

Course Code
GEOG 2122A/B
Dartmouth- Hitchcock
Study Guide

of 1
Earth Sciences 1022b Lecture Brief 8 Jan 15
Why? Geology (study of Earth) is important for energy and natural resources, solving
environmental problems, building cities and highways, predicting and protecting
against natural disasters like earthquakes, volcanic eruptions, landslides, floods
Uniformitarianism: fundamental principle “the present is the key to the past”
How long? geologic time is measured in billions of years
Where and How? After the Big Bang (~14 billion years ago) Earth may have formed by
the nebular theory: ~5 billion years ago a solar nebula of hydrogen and helium
gravitationally contracted into a rotating disc with our Sun at the centre, and the
planets and moons revolving around it
within the disc, Earth evolved through many collisions of rocky and metallic fragments
into a rocky sphere divided into a dense core, large mantle, and lighter crust
Plate Tectonics: the crust and uppermost mantle eventually split into rigid plates of
lithosphere (sphere of rock) that move over Earth’s surface above the soft,
convecting asthenosphere (weak sphere) by Continental Drift, based on...
fit of the continents - e.g. South America, Africa and other continents fit well together at
900 m depth which coincides with the edge of their continental shelves
fossil evidence - same type and age found on continents separated by ocean basins
rock types and structural similarities - match when continents are fit back together
paleo climates - evidence of ancient glaciations in warm areas of today - show the
pattern of a single ice sheet if continents are refitted back together; also, ancient coal
fields that formed in tropical swamps now occur in areas of cold climate
most geologic activity (e.g. earthquakes, volcanoes) occurs at plate boundaries;
especially at convergent boundaries where denser oceanic lithosphere descends
beneath lighter continental lithosphere; at depth it melts to produce magma which
rises to the surface and erupts as volcanoes which in turn are eventually eroded and
the sediment carried by streams to the ocean again
Earth System and Rock Cycle: Earth is a dynamic planet (system) of interacting
hydrosphere, atmosphere, biosphere, and geosphere (solid earth); matter
(molecules) is recycled with changing conditions of depth (pressure), temperature,
and rock type within Earth’s crust (e.g. convergent boundaries)
the rock cycle and plate tectonics together produce many different types of rocks that
are made up of different minerals that we will study in detail next class