Transcript Introduction to Atmospheric Science, PHSC 3223

PHSC 4013, Earth Science
Mr. Brian M. Cudnik,
Instructor
9 September 2008
Earth Geology vs. Planetary Geology
• We will study the planets in more detail later,
but it is useful to mention the parallels between
Earth geology and planetary geology
• By studying the processes that shape Earth’s
surface both from without and from within, we
gain the following:
– We learn about the nature of these processes
themselves and their origins
– By so doing, we can look for similar results on other
planets and infer past geologic history for that world
– The following summarizes the geologic processes
found on Earth (Note that these are external
processes, we touched upon internal processes last
time).
• The Rock Cycle gives rise to three main types of rocks,
based on their origins or means of formation
– Igneous rocks originate from cooling and crystallization of magma
from inside the Earth: Extrusive or volcanic igneous rocks form
when magma is forced to the surface; Intrusive or plutonic
igneous rocks are formed when magma cools inside the earth.
– Sedimentary rocks result from the compaction and cementation of
sediments formed on the surface by weathering, erosion, and
deposition processes.
– Metamorphic rocks are formed when pre-existing rock is altered or
metamorphized by extreme heat, pressure, and chemically active
fluids.
• Rocks are classified by their texture and mineral
composition; the rate of cooling of igneous rocks
determines the size of the crystals that make up the rock
(fast cooling means tiny crystals, slow cooling means
larger crystals).
• Some of the most important accumulations of metallic
mineral resources are produced by igneous and
metamorphic processes.
• Internal processes also occur to shape the face of
the earth: volcanism and mountain building get their
energy from Earth’s interior heat
• Differential weathering can occur depending on key
variables that can affect its rate: climate, heat, and
moisture patterns; chemical composition of the rock;
and the degree of jointing and fracturing that occurs
in the rock.
• Mass wasting may be rapid or it may be gradual, and
it may involve wet or dry materials.
• The following are factors that influence changes in
gravitational stresses on the materials:
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water saturation of slopes,
oversteepening by erosion or human activities,
earthquakes, or
vegetation removal.
The Forces that Shape the Earth
both Inside and Out
• So far we have considered the materials that make up the Earth
and briefly looked at its internal structure
• We will look at the forces, both from the outside and from the
inside, that shape the Earth as we know it.
• The primary driver of the external sculptors of Earth’s surface is
the Sun, driving the Atmosphere and the Ocean resulting in the
following mechanisms
– Weathering- the mechanical breakdown of rock by wind and water
– Mass Wasting-the transfer of weathered rock, soil, and sediment downslope
under the influence of gravity
– Erosion-incorporation and transport of surface materials by wind, water,
etc. (can you think of others, such as tornadoes and trees?...)
The Forces that Shape the Earth
both Inside and Out
• Agents of external weathering, erosion, and mass wasting
include the following (don’t worry about memorizing the
various types of stream and river drainage patterns…)
– Streams and rivers, lakes and oceans, and groundwater
– Glaciers and how these change the landscape
– Rain, snow, hail, sleet, accumulation, melt
• The forces that shape the earth from inside have a common
driver: the internal heat of our planet
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Review of the static and dynamic aspects of the interior of Earth…
How do we know what the inside of the Earth is made of?
Review of how this came to be over geologic time…
The vents of heat at the surface include volcanoes and plate boundaries
Plate Tectonics
• The process of Plate Tectonics plays a major role
in the shaping of Earth’s surface over long time
spans
• Plate tectonics describes the Earth’s crust as being
broken into some 27 plates, great and small
• The plates consist of lithospheric crust afloat on a
“sea” of asthenosphere
• Heating from below drives currents in the
asthenosphere which in turn carries the plates
along
Evidence for Plate Tectonics
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Shapes of the Continents
Fossil Record and extant species distribution
Mineral and Rock distribution
Remote sensing shows:
– Continents moving at the rate of 1cm per century
– Mid-sea floor ridges producing new oceanic crust (sea
floor spreading)
– Magnetic field imprint evidence in sea floor…
Types of Plate Interactions
• Divergent plate boundaries
• Convergent boundaries (mountain-building,
some types of volcanoes)
• Transform boundaries (earthquakes)
In Summary…
• External Energy Source—the Sun
– Weathering, Mass Wasting, Erosion
– Agents include Wind, Water, Landslides /
Avalanches, Tornadoes, ice, rain, hail, etc.
– The Sun also drives: the Water Cycle,
Atmospheric currents and Weather, Ocean
currents and climate, the Freeze and Thaw of
ice caps, snow, glaciers, etc
In Summary
• Internal Energy Source: the Earth (heat
from within)
– Plate Tectonics: Earthquakes, volcanoes, rock
deformation and mountain building
– Heat rising from the interiors of the Earth left
over from the initial formation
The History of the Earth
• Two types of dates used by geologists to
interpret the history of the earth include:
– Relative dates—puts the events in their proper
sequence of formation
– Numerical dates—which pinpoint the time in
years when an event took place
• Relative dates established by the law of
superposition
The History of the Earth
• Two types of dates used by geologists to
interpret the history of the earth include:
– Relative dates—puts the events in their proper
sequence of formation
– Numerical dates—which pinpoint the time in
years when an event took place
• Relative dates established by the law of
superposition, principles of original
horizontality, cross-cutting relationships,
inclusions, and non-conformities.
The History of the Earth
• Correlation-matching up of two or more geologic
phenomena in different areas—most common
example is the fossil record.
• Radioactivity is the spontaneous break-up (decay)
of unstable atomic nuclei and come in three
common types:
– Emission of alpha particles (helium nuclei) from the
nucleus
– Emission of beta particles (electrons) from the nucleus)
– Capture of electrons by the nucleus
The History of the Earth
• Radioactive decay
– An unstable isotope or Parent will decay and form
stable daughter products
– Half-life is the length of time for half of a given sample
to decay to daughter products
• If the half-life of an isotope is known and the
parent/daughter ratio can be measured, the age of
a sample can be calculated
• However, not all rocks can be dated
radiometrically
– An example is a sedimentary rock bed with particles of
many ages weathered from different rocks formed at
various times
– Dates can be assigned by relating these rocks to datable
igneous masses like volcanic ash beds.
Introduction to Critical Thinking
Skills
• In addition to the regular course material, I will be
providing supplementary material detailing critical
thinking processes
• The introductory sheet will be provided separately in a
word document
• Each week, a Cognitive Skill and Affective Attribute will
be highlighted briefly in class and in the class notes
• Due to time and scope limitations, we will not do the
exercises associated with these. We do them as part of
another course, Introduction to Atmospheric Science
• The material comes courtesy of the American
Meteorological Society
Cognitive Skill of the Week: Interpretation
Interpretation is "to comprehend and express the meaning or
significance of a wide variety of experiences, situations, data, events,
judgments, conventions, beliefs, rules, procedures, or criteria."
(American Philosophical Association) A learner who looks at a
weather map and is able to describe weather patterns, such as the
circulation around high and low pressure centers, is demonstrating
interpretation.
Affective Attribute of the Week: Inquisitiveness
Inquisitiveness is the inclination to be curious, to ask questions, and to
thirst for knowledge. A critical thinker spends considerable time
wondering about things and typically seeks more explanation and
understanding. An inquisitive person is generally probing the
unknown and habitually finds that seeking answers to questions
invariably leads to more questions. A learner who has interpreted
wind patterns on weather maps related to centers of high and low
pressure begins to wonder why such circulation happens. That
person is demonstrating inquisitiveness.