Download Eras, periods and epochs Dating by radioactive

Planetesimal/nebula hypotheses
(dust-cloud hypotheses)
Basis: observations of other systems
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Collision or Large star in Milky Way exploded
Nebula (cloud of dust and gas) results
H and He condense into Sun
Other elements form disk of matter around sun
Disk slowly accretes into clumps (planetesimals)
planetesimals → planetoids → planets and
satellites
Eras, periods and epochs
Superposition: youngest rocks superimposed on older rocks
“Relative time”
Dating by radioactive isotopes
Half-life: time for ½ of unstable isotopes to decay
“Absolute time”
Uniformitarianism:
“The same physical processes active in the environment
today have been operating throughout geologic time”
Hutton (1795), Lyell (1830)
Source: University of Calgary
Mineral
A natural, inorganic compound with a
specific chemical formula and a
crystalline structure
Examples
silicates (quartz, feldspar, clay minerals),
oxides (eg., hematite)
carbonates (eg., calcite)
A rock is an assemblage of minerals
bound together
• Igneous (solidify and crystallize from
molten magma)
• Sedimentary (settling)
• Metamorphic (altered under pressure)
• from magma
(molten rock
beneath the
surface)
• intrusive or
extrusive (from
lava)
Existing rock is digested by
weathering, picked up by erosion,
moved by transportation, and
deposited at river, beach and ocean
sites.
Laccolith
Sill
Dike
Lithification follows (cementation,
compaction and hardening)
Batholith
Laid down in horizontally-layered beds
Conglomerate
Sandstone
Siltstone
Shale
Limestone
Coal
largest clasts
sand cemented together
derived from silt
mud/clay compacted into
rock
calcium carbonate, bones
and shells cemented or
precipitated in ocean waters
ancient plant remains
compacted into rock
Any type of rock is transformed, under
pressure and increased temperature
Shale
Slate
• Harder and more resistant to
weathering
Granite
Gneiss
Basalt
Schist
Limestone, dolomite
Marble
Sandstone
Quartzite
• Compressional forces: (i) collision of
plates, (ii) rock thrust under crust,
(iii) weight of sediment above
•Continents are adrift due to convection
currents in the asthenosphere
•Mantle drags around the continents
•225 M BP: Pangaea
Fossil Record (plant and animal)
Distribution of marsupials vs. placentals
Age of mid-oceanic ridge magnetic stripes
Age and thickness of oceanic crust
Subduction zones
“Ring of fire”
Divergent Boundaries (constructional)
Convergent Boundaries (destructional)
Transform Fault Boundaries
URL: http://pubs.usgs.gov/publications/text/Vigil.html
Earthquakes
Source: USGS
Two types of crust “float”
on the upper mantle:
• oceanic crust (heavier, sinks lower)
• continental crust (lighter, floats higher)
Three types
of plate convergence
• oceanic – continental
• oceanic – oceanic
• continental - continental
Oceanic – continental plate convergence
Nazca plate – South America plate
Oceanic – oceanic plate convergence
New Hebrides Trench near Vanuatu
Earthquake Motion
Continental – continental plate convergence
India/Eurasia plate collision
(forms Himalayan Mountains)
Historical seismic activity in Canada
http://www.pgc.nrcan.gc.ca/seismo/recent/50.htm
http://www.ctv.ca/servlet/ArticleNews/story/CTVNews/1099405935151_16/?hub=Canada
1906
San Francisco
Earthquake
Mercalli
Richter
Liquefaction and slumping
Anchorage, Alaska - 1964
1964 Alaska earthquake damage
map: modified Mercalli scale
III - IV
V
VI
VII
VIII - X
Earthquake-proof buildings
Tsunami
(seismic wave)
Is a major earthquake in
California, Alaska or Japan of
any concern thousands of
kilometers away, in Hawaii?
The power of a tsunami
Volcanoes
Effusive eruptions
(gentle flows, lots of lava)
• cinder cones
• shield volcanoes
• plateau basalts
Explosive eruptions
(viscous lava, trapped gases)
• composite volcanoes
• calderas
Cinder cone
Big Cinder Butte,
Craters of the Moon, Idaho
Shield volcano
Mauna Loa, Hawaii
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Low viscosity magma
Gases readily escape
From this magma
Effusive eruptions
- forms small hills, less than 450 m high
- black scoria rock with air bubbles
Kilauea, Hawaii
Seamounts
Hot spot
Composite volcano
Shield/Composite Comparison
Plateau basalts
Live Photo of Mt. St. Helens!
Mount St. Helens: the day before
http://www.fs.fed.us/gpnf/volcanocams/msh/
Flooding (from steam-melted ice and snow)
Caldera
Four years later
Crater Lake, Oregon
Volcanic hazards and effects
6600 years ago
windblown ash
landed in Calgary
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hot ash (pyroclastics)
steam and gas explosions
lava flows
poisonous gases (carbon dioxide, sulfuric acid)
landslides
tree blowdowns
lahars (steam-melted ice and snow cause flooding
and large mudflows)
• increase in atmospheric dust (decreased global
temperatures)
Volcanic benefits
• new fertile soils
- Hawaii, Philippines
• geothermal energy
- Iceland, Italy, New Zealand
• new real estate
- Iceland, Japan, Hawaii
Diamond-bearing kimberlite pipe