Transcript Slide 1

Stories from
the Ocean Floor
Developed by J. Fechhelm using materials from the 2007 “School of
Rock”
sponsored by the Joint Oceanographic Institutions
and the Integrated Ocean Drilling Program at Texas A&M
University
The Deep Sea Drilling Project was begun in 1964 and
was designed to investigate the evolution of ocean basins
by core drilling of ocean sediments and underlying
oceanic crust.
The data used in this activity were taken from cores
collected by the drill ship “Glomar Challenger”, on a
cruise in 1968. The
Deep Sea Drilling Project
was the first of three
international ocean
drilling programs
that have continued right
up to today.
http://pubs.usgs.gov/gip/dynamic/glomar.html
This map shows where the three ocean drilling programs have drilled
into sediments on the seafloor and the Earth’s crust.
http://iodp.tamu.edu/scienceops/maps/poster/combined.html
Remember
that the
plates on the
surface of
the Earth
have
changed
position
throughout
the Earth’s
history.
These
diagrams
show what
the Earth
looked like
80 million
years ago.
When scientists drill into the sea floor, the oldest sediments are at
the bottom, and the newest sediments, those that are just settling
to the bottom of the ocean, are at the top.
Illustration of core, section, and sample numbering. From: Shipboard Scientific
On the third trip of the Glomar Challenger (Leg 3) the
crew drilled holes at 10 different sites along an oceanic
ridge between Africa and South America.
What they found
astonished many around
the world and opened up
a whole new area of
scientific investigation.
http://geology.wr.usgs.gov/parks/province/atlantpl.html
The numbers
show the drill
sites from Leg 3.
The spots along
A, B and C show
drill sites along
the Mid-Ocean
Ridge.
When ocean cores are drilled, scientists can
then look at the fossils of ancient organisms
found in the sediments.
From years of study, scientists can tell the
age of sediments by looking at the fossils.
Some organisms, or their fossils, are used as
indicator species.
This means that if those organisms are
found, scientists can tell the age of the
sediments, or when they were deposited on the
sea floor.
There are 3 main groups of microscopic
organisms that scientists use.
Nannofossils
Very tiny (0.2 to 2 microns!)
1 micron (or micrometer)= 1 X 10 -6 or 1/1,000,000
Often occur in massive “blooms” in the ocean – so
large they can be seen in satellite pictures!
http://www.biol.tsukuba.ac.jp/~inouye/ino/etc/coccolithophorids.jpg
Diatoms
20 to 200 microns - up to the size of a grain of sand.
Also can occur in massive “blooms” in the oceans.
htttp://k55.nu.edu/resources/NU/collateral/newsletterPhotos/diatoms.jpg
Foraminifera
100 to 10000 microns.
Very important in the dating of ancient deep sea
sediments.
http://www.palaeos.com/Eukarya/Units/Rhizaria/Images/Foraminifera.jpg
http://www.fathom.com/course/10701050/foraminifera.jpg
Now back to Leg 3 of the Glomar Challenger!
Let’s look at the actual data.
Let’s narrow our focus.
Site Number
Age of sediment above basement (in
millions of years)
14
40 m.y.
15
24 m.y.
16
11 m.y.
17
33 m.y.
18
26 m.y.
19
49 m.y.
20
67 m.y.
21
>76 m.y.
On your map, next to each site number, write
the age of the sediments. (Remember, these
sediments are those at the very bottom, right
above the rock.)
Answer questions 1 to 3.
Now let’s make a model of this!
And then answer analysis question 4, 5 and 6.