Earth’s Changing Surface – Part 1 Notes
Formation of the Earth
Plate tectonics –
- creates land formations
o ex. mtns, valleys, ridges, trenches, basins
- creates major events
o earthquakes
o volcanic eruptions
o tsunamis
- most action occurs at plate boundaries
- 3 types of interaction:
o Spread apart
o Slide along each other or collide
o Overlap – one may sink another
- Subduction zone
o Overlapping plates
o Volcanoes
o Trenches
- Convergent zone
o Plates come together
o Mtns
o Volcanoes
o Trenches
- Diverging zone
o Plates pulling apart
o Rift valleys
Trenches – deepest parts on Earth
- subduction zones
- Pacific holds deepest trenches (5)
o Marianas Trench (10,911m)
 ~70 km wide
 Mt. Everest would fit inside the trench with room to
spare
o Tongo Trench (10,882m)
o Kuril Trench (10, 542m)
o Philippine Trench (10,540m)
o Kermadec Trench (10,047m)
- Ring of Fire
o Pacific’s large number of volcanoes due to the interaction
of plates
o Subduction zone
Parts of the Earth
1 – Crust
2 – lithosphere – solid crust & upper mantle
3 – asthenosphere – melting rocks
- lithosphere floats on this
4 – outer core
5 – inner core
- interactions of plates creates all the land forms from their
activity
New floor forms – mid-ocean ridges
- cools quickly outside of Earth
- redeposits outside & moves further away
- called seafloor spreading
Seamounts – inactive volcanic cones
- possibly old volcanoes
- extend out above the ocean are called volcanic islands
o Hawaii
Mining the ocean floor – many petroleum & gas deposits in continental
shelf
- 20% of world’s oil come from here
- Placer deposits – deposits are too heavy to travel too far from
where the river dumps into the ocean
- They sink & build up
- Deep ocean deposits
o From inside the Earth, hot water & molten minerals seep
into the ocean & deposits when they hit cooler water
(temps)
o Ex. Maganese nodules
 Build up around shark’s teeth over millions of years
 Rich in manganese, nickel, cobalt
Fossils and Studying Earth’s Past
Fossils
Fossil formation – evidence such as the remains, imprints, or traces of once
living organisms
- preserved in rocks – called fossils
Fossils help: - find out when life began
- plants and animals first on land
- identify specific animals
- when they lived
- where they lived
- how they lived
Conditions to fossilize: - organisms has to be protected from microbials
- hard parts to help with fossilization (bones, teeth, etc.)
- needs to be covered quickly
http://geology.about.com/library/bl/images/blfossilindex.htm
http://www.uky.edu/KGS/education/fossil_trip2.htm
http://www.uky.edu/KGS/education/fossils_form.htm
Types:
- petrified remains – hard & rocklike
o some parts have been replaced by minerals
o ex. Water w/ quartz flows through bones
 water dissolves Ca and deposits quartz
 harder than Ca so it becomes rocklike
- carbonaceous films – organisms are made of carbon
o piled up sediments create heat & pressure conditions
for dead organisms
o leaves a thin film of carbon forming an outline of the
organism
o ex. Carbonization – to process of chemically
changing organic material
 forms coal – completely carbonized
 millions of years
http://educmoon.tosm.ttu.edu/edit3318/2009Summer/Cude/resource_page.html
- molds & casts
Organism dies
Squeezed
together – water
& air finds way
to hard parts
Falls into soft
sediments – ex.
mud
Hard part
dissolves- leaves
hallow place
(mold)
Buried by more
sediments
Sediments fill
mold & harden
into rock (cast)
- original remains – amber trapped insect (sticky resin from
trees that hardens
o frozen ice – organisms frozen from environmental
temps or trapped in ice
o tar seeps – (La Brea) – organisms that became stuck in
tar and trapped and suck in pit
http://www.willoughbyeastlake.k12.oh.us/willoughby/Marinelli/HoltChapterMaterials/Fossils/TypesOfFos
sils.pdf
(FoxNews.com)
Frozen Baby Wooly Mammoth – estimated
six months old when died. About 10000-40000 years old
http://www.tarpits.org/education/guide/index.html
- trace fossils – tracks & other evidence or animal activity
o can guess size, weight and age
o ex. Apatosaurus – larger size footprints surround
smaller size
 indicates adults protecting young
- index fossils – shows evolving, unchanging, or dying out
of species
o species that lived on Earth for a short period of time
o abundant
o covered wide geographic areas
o help tell age of rock layers
Fossils & Ancient Environments
- rocks in Antarctica contain tropical plants
- hypothesize/infer that at one time, Antarctica was in a
tropical region
- brachiopods – lived in shallow seas
o found in rocks of the Midwest US
o infer the Midwest was covered once by water
- can give input to environment, climate, rock dating, and
animal
behavior
Relative Age of Rocks
Principle of Superposition – youngest layer on top
Ex. Topsoil – most recent decomposed organisms
Bedrock – oldest – started layers
Relative Dating – uses sedimentary, igneous & metamorphic rock layers &
how they are
positioned to gauge time lines
- not worried about exact dates – more concerned with
sequencing
- index fossils help when layers are hard to determine
Uncomformities – when layers are missing in a soil profile
- gaps in rock formations of layers
- happen when erosion removes existing layers
- happen when no deposition occurs to form new layers
Angular conformity
Disconformity – when erosion occurs in sedimentary rocks and
new layers fill
in those gaps
Nonconformity – when metamorphic or igneous rocks are uplifted
and eroded
- surface between the two rocks
Correlation – geologists use layers of rock in different places and
compares
or “correlates” them
- use of fossil evidence supports correlating
Absolute Age of Rocks
Absolute dating – a method used to determine the age (in years) of an object
- uses atoms in rocks and other objects to determine age
- uses Radioactive Decay:
o periodic table of elements
o found naturally at room temp as a solid, liquid or gas
(state of matter
o color on table indicates metal, non-metal, metalloid
o each atom has unique properties including the
atomic #
 indicates the # of protons in the nucleus of a
specific atom
 unique only to that particular element
 different # of protons, different atom(element)
 neutrons can vary but typically are the same #
as the protons
 when # of neutrons changes, an isotope is
formed
 isotope – atom that has a different # of neutrons
than protons in the nucleus of a particular atom
of an element
 may indicate radioactive decay
Atom found in nature
Neutrons change – different # of neutron but same # of protons
Isotope forms
Neutron breaks down and creates a proton and possibly a radioactive particle
Different # of protons in nucleus
Completely different type of atom (element)
Radioactive Decay
- 3 types
o Alpha
o Beta
o Gamma
o http://library.thinkquest.org/3471/radiation_types_bo
dy.html