Chapter 1.docx

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22 Apr 2012
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Chapter 1:
What is Geology?
- Geology” is derived from the Greek words geo & logos and means “the study of the Earth.”
- The first known geological map was created by ancient Egyptians over 3000 years ago BUT the scientific
discipline of geology as we understand it today came into being only in the late 18th century.
- The Industrial revolution in Northern Europe created a growing demand for energy & minerals such as
coal, limestone, iron and water.
- A geologist finds & explores resources on planet earth.
- One of the earliest detailed geologic maps was published in England in 1815 by William Smith (The
father of English geology).
- In North America, geological mapping began in the mid-nineteenth century.
- Sir William Logan became the founding director of the Geological Survey of Canada in 1842.
- In the late 17th century, It was believed that the Earth was only about 6000 years old.
- Now, the age of the Earth has been determined to be at least 45000 million years old.
- The movement of continents on the Earth’s surface was suggested early in the 20th century by the
German meteorologist- Alfred Wegener-> who wrote continental drift in 1912.
- Wegener recognized that today’s continents had previously been clustered together in a large land mass
but had subsequently moved apart; Pangea (all of the lands).
- Rock record: helps to explain how we are able to find matching rocks in Indian & Asia when there is an
ocean between them now.
- Subduction: the process where the sea floor slides beneath a continent or island arc.
William Smith:
- Produced the first comprehensive geological map of England in 1815.
William Logan:
- Created the first systematic layout of the geology of Canada.
Alfred Wegener:
- A German meteorologist who suggested the theory of continental drift.
J. Tuzo Wilson:
- First Canadian to complete a degree in geophysics.
- He is remembered for his contribution to the development of the plate tectonics theory. (transform
faults & hot spots)
- “transform faults”
- The earth is estimated to be at least 4.55 billion years old.
- Fossil rocks: 545 million years ago.
- Reptiles: 230 million years ago.
- Humans have been here only about the last 3 million years.
- “Rapidly” to a geologist means a few million years.
- “recent” means something could have happened within the past several years.
- Geoscientists work in the field to find prospective money making minerals & diamonds analyze the
chemistry of rock/minerals.
- Mineralogists- study minerals
- Petrologists- study the makeup of rocks & how they form
- Seismologists- study how to measure & mitigate earthquake activity
- Paleontologist- study the remains of dinosaurs
- Hydrogeologists- study the water which transmits sediments in order to protect them
- Environmental geoscientists- study the challenges being faced as urbanization grows.
- Geomaticians- collect, organize, analyze and create images from any spatial and geographic data available
in digital forms.
- Geoscientists use a scientific method:
- Problem/Question Methodology/Data collection Analysis/Interpretation Hypothesis/Hypotheses
Testing Theory
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The Solar System:
- 15 Ga universe was said to be formed by clumping together gas an debris.
- Our solar system was created from a cloud of hydrogen & helium gas & dust particles called a nebula
probably formed from the nova explosion of a red giant star.
- Formed to make a bulbous core & a flattened disc within the outer edges of the disc rocks & metals
formed via accretion to form planetismals
- Terrestrial planets- Mercury, Venus, Earth- planets that are small, rocky, close the sun & high in density.
- Jovian planets- Jupiter, Saturn, Uranus, & Neptune planets which have low densities.
- Larger planets were able to attract & hold larger amounts of lighter gases such as hydrogen & helium.
- The bodies nearest to the centre of the nebula would have experienced higher temperatures thus
retaining smaller percentages of materials that are easily vaporize.
- Outer disc planets were colder thus collecting more ice & rocky materials.
- The Earth was formed & was affected by impact craters.
- The moon was created from the debris that was flung off into space.
- Differentiation the process of zoning of different materials within a planet- the heavier materials settled
towards the core of the Earth like iron & nickel whereas the lighter materials like silica & oxygen settled to
the surface.
- Early heating of planetary interiors caused much volcanic activity.
Formation of the Early Atmosphere
- Predominantly formed from water & gaseous elements released during out gassing.
- Earths’ early atmosphere was rich in carbon dioxide released from volcanoes creating highly acidic rain &
ocean waters which life forms had adapted to.
` As the life forms began to evolve they separated carbon dioxide into carbon and free oxygen.
Internal structure of the Earth
- Innermost core- composed of iron alloy (iron with nickel & silicon)
- Mantle- composed of iron combined with magnesium (forming a rock called peridotite- volumetrically the
most common rock on Earth)
- Behaves like wax & can slowly flow & change shape as it is moved around in enormous convection cells.
- Causes stress within the overlying layer.
- Breaks the crust into larger pieces into lithospheric plates.
- Plates are pushed around the surface over a weak layer called asthenosphere.
Can either be separate at spreading centres- hot mantle erupts to form oceanic crust
Places also collide one is pushed below another to be recycled back into the mantle along subduction
zones causing active volcanoes & earthquakes
When they slide past each other it’s called transform plate boundaries
Continental collisions are also preserved in the geologic record as suture zones, terrane boundaries &
mountain ranges.
Outer crust- composed of “lighter” rocks such as basalt & granite
Early Life Forms
- Single celled organisms called prokaryotes
Were able to trap sediment & grow organic structures called stromatolites
- 600 Ma- Cambrian explosions of organisms with more complex structures with backbones and hard shells.
Richest repositories of Cambrian age fossils is in the Burgess Shale.
Could have been a response to dramatic changes in geography and climate creates by the break-u of
the super continent Rodinia.
The Rock Cycle
- The internal & external forces are interacting with each other to create a dynamic cycle of Earth’s surface.
- Magma Molten rock
Igneous rock- solidified magma
If magma is brought to the Earth’s surface by a volcanic eruption, it may solidify into an extrusive
igneous rock.
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