Transcript Continental Margins

Sea Level and Climate Changes
on NJ’s Continental Shelf
Dr. Michael J Passow
Like a fiddler on the roof, it may seem strange
to look at layers of underwater sediments and
sedimentary rocks off the coast of New Jersey to
discover how sea level and climate has changed
over the past 35+ million years
But that’s what today’s program is about
Where the ocean meets the land is not
the real edge of continents
• Oceans cover parts of what once was land,
and, in some places, what is now land was
once part of the oceans
• The zone where continents and oceans meet
is called the continental margin
Active Margins
• Some coasts are geologically active
• Many of these have deep trenches or are
seismically active (have many earthquakes)
• The west coasts of North and South America,
from Tierra del Fuego to the Aleutians, are
active margins
http://en.wikipedia.org/wiki/Active_margin
Passive Margins
• Other coasts show little geologic activity and
are called passive margins
Much of the East Coast of North America, from NJ to FL
and continuing along the Gulf Coast to TX, is a passive
margin
Active margins
• are relatively narrow
• have many earthquakes
• drop off into deep
trenches or have volcano
chains
• form the “Pacific Ring of
Fire” that extends from
New Zealand through the
Philippines, Japan, Alaska,
the Cascades, Middle
America Trench, and
Peru-Chile Trench
Passive margins
• are much wider
• have few earthquakes
and no trenches
• along the Atlantic and
Indian coastlines
• often have coastal plains
and continental shelves
• the world’s great rivers
drain across passive
margins (Amazon, Nile,
Congo, etc.)
Profile of a Passive Margin
Passive margins often have relatively flat
continental shelves, steeper continental slopes,
and continental rises that gradually blend into
flat abyssal plains
The NJ continental shelf is about 120 km (75
mi) wide. At the shelf break, it is only about
200 m deep.
http://clasticdetritus.com/2007/12/02/sea-floor-sunday-6-hudson-shelf-valley/
The Hudson Canyon
• “underwater Grand
Canyon”
• More than 700 km long
• As much as 12 km wide
• Descends from about
100 m to more than
2,200 m below sea level
• http://en.wikipedia.org/
wiki/Hudson_Canyon
Other Submarine Canyons
http://en.wikipedia.org/wiki/Submarine_canyon
• West Coast canyons
start very close to CA
beaches and descend
rapidly
Although “passive,” the NJ Conshelf
records many changes
• During glaciations,
more is exposed land
• Evidence of forests in
what is now the sea—
mastodont teeth snared
in trawler nets
• Outwash and other
glacial features now
features of sea floor
• When sea level is higher,
locations now on land
submerge
• Potential for significant
changes over next
century
• Re-working of sediments
during major storms,
including Sandy
Rutgers University Research about the
NJ Continental Shelf
• IODP Expedition 313
(2009)
• Objectives included
learning about changes
in sea level over past 35
million years, and
climate changes during
this period
http://www.eso.ecord.org/expeditions/313/
313.php
www.rucool.marine.rutgers.cool
How Did We Get to the Ability to
Conduct Such Research
• It all began with Marco Polo in 1300
People began to sail in search of the wealth of
the Orient, rather than merely go in caravans
• Great coastal kingdoms of West and East Africa
In 1400 and 92….
• Columbus accidentally discovered the “New
World”
• Western European countries “claimed” vast
territories for their empires
“Pioneers” of the 18th & 19th Century
• Capt. James Cook’s
HMS Resolution (1770s)
• Charles Darwin and HMS Beagle (1830)
• HMS Erebus and HMS Terror (1840s)
• Focus on discovery and mapping
Matthew Fontaine Maury
• Produced “The Physical
Geography of the Sea”
(1855)
• Collected data from
ship logs, collated into
one of the most useful
publications ever
• First book to provide
navigators with
information about the
oceans
Invention of the Telegraph Opened New
Demands for Rapid Communication
• Transcontinental, then, transAtlantic
• “Great Eastern” (1869)
http://raoulpop.files.wordpress.com/2009/02/1858-telegraph-cable-map1.jpg
New Need to Understand the Features
Beneath the Ocean Waves
• “HMS Challenger”
(1872 – 1876)
• Used weighted piano
wire, rather than ropes
• Discovered great
trenches, flat plains,
large mountains
http://life.bio.sunysb.edu/marinebio/ch_01.jpg
SONAR
• 1920s – “Meteor” first
research ship to use
SOund
NAvigation and
Ranging devices
• Extensive anti-sub
warfare in WW II
• Created vast archive
of echo-soundings
Bruce Heezen, Marie Tharp, and
Physiographic Maps of the Sea Floor
http://www.roebuckclasses.com/maps/physicmap/ocean/MapBBFull.jpg
Earlier Studies
• Veitch & Smith (? 1939)
• Early Lamont Geological
Observatory research
tested technology to
probe beneath the sea
floor
• Many short cruises in
NY Bight
Calypso (Jacques Cousteau, 1940s-80s)
SCUBA,underwater living experiments,
popular TV specials
http://www.cousteau.org/about-us/vessels
Wood Hole Oceanographic Institution (WHOI)
• R/V Atlantis and “Alvin”
• R/V Knorr
http://www.whoi.edu/page.do?pid=7121
Scripps Institution of Oceanography, UCSD
• R/V Roger Reveille
• R/V Melville
http://shipsked.ucsd.edu/Ships/
NOAA and US Navy Research Vessels
• Ronald Brown
• Bruce C. Heezen
• Ka'imimoana
Scientific Ocean Drilling
• First proposed in 1957 by Walter Munk (SIO)
• Exploratory drilling in early 1960 proved the
feasibility of the technology
• “Glomar Challenger” built in 1967 for the
Deep Sea Drilling Project (DSDP)
Confirmation of the Seafloor Spreading
Hypothesis
• Almost as soon as the “Glomar Challenger”
began its scientific drilling efforts, spectacular
results were obtained!
• During Leg 3 (1968), a series of cores confirmed
that the age of the ocean floor varied,
becoming progressively older on opposite sides
of the mid-ocean ridge
http://www.oceanleadership.org/classroom/plate_tectonics_nannofossils
ODP: Ocean Drilling Project
1983 - 2003
• DSDP expanded and evolved into the ODP
• “JOIDES Resolution”
• More about the ODP can be found at http://wwwodp.tamu.edu/index.html
IODP: Integrated Ocean Drilling Program
2003 - 2013
• International marine research program that
explores the Earth's history and structure as
recorded in seafloor sediments and rocks, and
monitors subsea floor environments.
• Greatly expands the reach of these previous
programs by using multiple drilling platforms,
including riser, riserless, and mission-specific,
to achieve its scientific goals.
IODP Also Uses Riser and Mission-Specific
Drilling Vessels
Riser vessel: “Chikyu”
http://www.iodp.org/riser-vessel/
Mission-Specific
Platforms
http://www.iodp.org/mission-specificplatforms/
Expedition 313
Shallow-water drilling of the New Jersey
continental shelf: global sea level and
architecture of passive margin sediments
http://www.eso.ecord.org/expeditions/313/313.php