The Dynamic Planet: Geology of the World
GEOLOGY (or “Earth Science”)
The study of the origin, structure,
composition and physical history of Earth,
together with the processes which have led
to its present state.
The science that deals with the dynamics
and physical history of Earth, the rocks of
which it is composed, and the physical,
chemical, and biological changes that it has
undergone and is undergoing.
Geog 1000 Introduction to Physical Geography Fall 2010 : Dr. Hester Jiskoot, University of Lethbridge
Fundamental stratigraphic principles Uniformitarianism Catastrophism
“Present is key to the past”
1. superposition of layers (strata) Continuing uniformity of existing Earth created through supernatural
2. original horizontality processes/physical laws responsible means and affected by a series of
for present & past conditions on earth catastrophic events
Earth is old Earth is young
Processes take time to form earth Catastrophic events form earth
James Hutton (1726-97) Cuvier (1769-1832)
- Father of geology Catastrophes are events with natural
Earth is in perpetual process of causes
formation & denudation Geologists now know that natural
catastrophes have had and have
Charles Lyell (1797-1875): some role in forming the Earth's
“Principles of Geology”: evidence from landforms and rocks/sediments.
geologic record for Uniformitarianism
Earth formed through gradual
Charles Darwin (1809 –1882) processes, punctuated by dramatic
Guiding principle = uniformitarianism Biological evolution through natural events ( volcanic eruptions,
earthquakes, floods, landslides)
Pre 2006: Oldest dated rock on earth
Acasta gneiss found in Northwest Territories, Canada
Dating methods: radioactive decay of Uranium and Thorium to Lead
The geological time scale
o n ye
ck: Boundaries of eons, eras, periods and epochs
e rsity rthern
Univ No evolvement/extinction of animal life forms
Gill e belt,
: Mc n
(20 08) ensto
nce uq g
global climate variations
3.96 billion years
Rock in National Museum for Natural Sciences, Smithsonian institute (Washington, DC)
plate distribution New in 2004:
544 M yr
International Cmtee on Stratigraphy
over geological http://www.stratigraphy.org
time PRECAMBRIAN deleted
ARCHAEAN Now EONS
4,500 M yr
Hadean eon 4.5 to 3.8 billion yrs ago
Solar System was forming (planetisemal hypothesis) today
Earth starts cooling
First Rocks form
Archaean eon 3.8 to 2.5 billion yrs ago
Earth's crust cooled enough continental plates began to form.
Oldest fossils date ~ 3.5 billion yrs ago (bacteria microfossils).
544 million yrs
Proterozoic eon 2.5 billion to 544 million yrs ago
First stable continents
First abundant fossils of living organisms (bacteria, archaeans, eukaryotic cells)
First evidence of oxygen build-up in the atmosphere 4,500 million yrs
Paleozoic Era 544 to 245 million yrs
Two of the most important events in the history of animal life:
1) Multi-celled animals underwent a dramatic "explosion" in diversity
2) the largest mass extinction in history wiped out approximately 90% of
all marine animal species
Mesozoic era 245 to 65 million yrs
Culmination of world fauna (except for insects): very different from previous eras.
First fossils of modern mammal and bird groups
Dinosaurs (+ ammonites, etc) evolve and become extinct
Lush terrestrial vegetation
Cenozoic era 65 million yrs to the present
146 to 65 My BP
Evolvement to modern times
>2.7 M yr Cyclic Ice Ages
Quaternary K/T boundary: marker of one of the extinction events
ASTEROID IMPACT Chicxulub crater at the bottom of Gulf of Mexico
World-wide thin layer of same sediment:
Upper "Fireball layer" ~ 3mm thick.
Lower "Ejecta layer“ ~ 2cm thick.
Layers mostly clay, with soot in upper parts.
See a video on http://videos.howstuffworks.com/science-channel/29285-100-greatest-discoveries-chicxulub-crater-video.htm
Earth diameter = 12750 km known by the ancient Greeks
20th century: planet earth is made up of 3 main layers:
What are the main stratigraphic principles? crust, mantle, and core
What are the geological time periods based on?
What are the main eras?
In which era did the dinosaurs live?
Why does the science of geology evolve so fast?
Excellent website on geological time:
Think of an egg
Magnetic field &
How do we know? Seismic waves
THE EARTH’S CRUST
Northern lights / aurora borealis
ISOSTACY & ISOSTATIC REBOUND ISOSTACY & ISOSTATIC REBOUND
THE PEOPLE BEHIND PLATE TECTONICS
Tectonic plates (~14) 1596 Abraham Ortelius, map maker: “Americas torn away from
Europe and Africa by earthquakes & floods"
1858 Antonio Snider-Pellegrini made ‘before’ and ‘after’ maps
1912-15 Alfred Wegener develops theory of continental drift
“understanding of how the Earth works requires input and
knowledge from all the earth sciences.”
1970s Theory of plate tectonics
Assumed convection cells in the mantle.
Below ~ 700 km, the descending slab softens, Break-up
becomes liquid, and loses its form.
Distribution of continental
plates and orogens
important for world climate
How do we know how to fit the jig-saw? Directions & rates of plate movement
Dated rocks/rocktypes/fossils - spatial distribution
Dated shorelines and marine deposits
Plate tectonics animations
Plate convergence/divergence/faulting Seafloor surface map
along a fault
Magnetic time record CRUSTAL FORMATION Orogenesis related to plate convergence:
1) Oceanic plate
2) Continental plate
3) Oceanic plate
Reading for Friday
What is the earth’s inner/outer core composed of and why is this important?
What types of plate boundaries are there?
Why is plate tectonics important (what other processes does it influence?)
Chapter 8 p. 273-280
What is Pangaea and why did it break up?