Time and Change & Rocks
and Structures
The Earth is about
4.5 billion years old.
From:
http://earth.geol.
ksu.edu/sgao/g100
/plots/1017_timeli
ne.jpg
Humans have been here for a VERY small part of Earth’s history.
How do we know the rest?
Some changes take place very
quickly!
From
http://www.em.gov.bc.ca/Mining/Geolsurv/Surficial/landslid/plate19.
jpg
http://www.nhoem.state.nh.us/mitigation/Mt%20St%20Helens%20w
o%20Frame.jpg
http://www.ferrara.com/columbia/attivita/viag
gi/arizona/scorcio%20grand%20canyon.jpg
Some are much more gradual, but still dramatic!
Absolute Age – The Actual time of
an event in Years
Relative Age – The Order that
events took place.
Families of Rocks
Igneous
Sedimentary
Metamorphic
Igneous – Were at one time in a hot,
liquid state.
http://www.bishopm
useum.org/exhibits/
pastExhibits/1997/t
reasures/large_imag
es/LOIHI2.jpeg
Magma is
molten rock
that is
underground
Magma
http://www.solarviews.com/raw/earth/earthfg2.gif
Molten rock on
the surface of
the earth is
called lava.
http://mahi.ucsd.edu/Gabi/erth10.dir/
lava-fountain.jpeg
http://www.southwestbirders.com/Hawaii_2002/lava%20flow%20i.jpg
http://www.gsfc.nasa.gov/gsfc/earth/pict
ures/co2/volcanom.jpg
When lava is blown out of a volcano
in small particles it is called volcanic
ash.
Rocks formed from lava or ash are
called volcanic rocks.
Basalt
http://z.about.com/d/geology/1/0/R/K/basalt.jpg
Obsidian
http://images.google.ca/images?svnum=10&hl=en&lr=&q=
obsidian
Pumice
http://www.gc.maricopa.edu/earthsci/imag
earchive/floating_pumice_big.jpg
Plutonic Rock – From magma that
has cooled and crystallized beneath
Earth’s surface.
Granite is
plutonic
http://www.vermontmarbleandg
ranite.com/granite/imggranite/g
4013rosaporrino.jpg
Solidifies as Plutonic Rock
http://www.uwsp.edu/geo/faculty/ritter/images/lithosphere/Earth_Structure/igenous%20landforms.jpg
When softer
sedimentary
rock is eroded,
it will
sometimes
leave the
harder plutonic
rock
formations.
http://wrgis.wr.usgs.gov/docs/parks/mojave/oncolith255x212.jpg
http://comp.uark.edu/~sboss/seds02.jpg
Sedimentary rock usually consists of
rock fragments such as mud, sand or
gravel that have been cemented
together.
Weathering – the physical or
chemical breakdown of rock exposed
to water, wind or ice.
The particles resulting from
weathering
-carried by rivers to the sea floor
-settle to form layers of sediment
-become sedimentary rock
If plant or animal remains are buried,
they may be preserved as fossils.
http://www.fox.uwc.edu/fossils/wisc/protax1.jpg
A Leaf Fossil
http://www.dll-fossils.com/Images/ginkgoalesleaf-web.jpg
http://www.mineraltown.com/infocoleccionar/imatges/rock_cycle.jpg
Metamorphic rocks were once
igneous or sedimentary. They have
been changed by heat and pressure
under the ground.
Shale (sedimentary) becomes
Slate (metamorphic)
Geological Structures
Fractures are
cracks in a body
of rock.
-can be formed by
water freezing,
earthquakes etc.
http://falcon.tamucc.edu/~peichhubl/Pages/Clinkermacro.jpg
http://geophysics.tau.ac.il/personal/shmulik/images/fault%20in%20Arava.jpg
A fault is a fracture along which
there has been movement. Faults can
be caused by earthquakes.
http://www2.nature.nps.gov/geology/usgsnps/klondike/mi8.2dikes240x247labeled.jpg
Dikes are igneous rocks formed in
rock fractures when magma is
squeezed upward and later cools.
http://www.indiana.edu/~geol116/week4/dike.jpg
http://www.geol.lsu.edu/henry/Geology
3041/lectures/04IgneousStructures/
4-22.gif
A dike at
Shiprock New
Mexico
http://www.gpc.edu/~janderso/images/folds.jpg
Folds occur when layers of
sedimentary rock are squeezed and
then buckle.
Erosion Surfaces
-when rock has been exposed to
weathering and erosion and later
reburied, the boundary is rough
and uneven.
http://www.oldstoneage.com/montetwhite/kadarimages/profile%20photo.jpg
Strata – means there are layers.
http://www.labyrinth.net.au/~tdp/images/strata.jpg
Identify the structures in the
diagrams on page 261 of the Text