The Sea FloorThe Sea Floor

GLG 101 - Physical GeologyGLG 101 - Physical Geology Bob LeightyBob Leighty

These lecture notes are very similar to the ones I use in my traditional classes. You’ll find they are loaded with imagery and streamlined text that highlight the most essential terms and concepts. The notes provide a framework for learning and, by themselves, are not meant to be a comprehensive source of information.

To take advantage of the global knowledge base known as the Internet, I have included numerous hyperlinks to external web sites (like the Wikipedia, USGS, NASA, etc.). Follow the links and scan them for relevant info. The information from linked web sites is meant to supplement and reinforce the lecture notes – you won’t be responsible for knowing everything contained in them.

As a distance learning student, you need to explore and understand the content more independently than in a traditional class. As always, I will help guide you through this learning adventure. Remember, email Dr. Bob if you have any questions about today’s lecture (rleighty@mail.mc.maricopa.edu).Leave no questions behind!

Explore and have fun!Explore and have fun!

These notes and web links are your primary “lecture” content in this class. Additionally, various articles are assigned each week to supplement this “lecture” information. I believe you’ll have enough information to reference without having to purchase a costly textbook.

The Sea FloorThe Sea Floor

Earth's early history - volcanic “outgassing” & asteroids/comets

Oceans include >97% of all water on Earth

Much of Earth’s surface is underlain by oceanic crust

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MappingMappingSea FloorSea Floor

Mapped mainly by sonar & satellite radar since WWII

Oceanic SedimentOceanic Sediment

Derived from land (terrigenous) – mud & sand

Derived from critters (biogenic) – chert & limestone

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Continental MarginsContinental MarginsPassivePassive

Example - east coast of N & S America, west coast of Africa

Minimal tectonism; no oceanic trench or volcanic arc

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Continental MarginsContinental MarginsPassivePassive

Continental ShelfContinental Shelf

Gently-sloping; underlain by continental crust

Shallow water (<135 m deep); affected by waves

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Continental MarginsContinental MarginsPassivePassive

Continental ShelfContinental Shelf

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Continental MarginsContinental MarginsPassivePassive

Continental SlopeContinental Slope

Deeper water (>135 m); not affected by waves

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Steeper than the shelf; submarine canyons

Continental MarginsContinental MarginsPassivePassive

Continental RiseContinental Rise Very deep water; grades into the abyssal plain of the deep

ocean Gently-sloping; underlain by oceanic crust

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Continental MarginsContinental MarginsActiveActive

Example - west coast of N & S America

Lots of tectonism; develop at subduction zones

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Continental MarginsContinental Margins

Dense, “muddy” underwater currents

Turbidity CurrentsTurbidity Currents

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Deep Ocean BasinsDeep Ocean BasinsAbyssal PlainsAbyssal Plains

Flattest places on Earth (deep-sea

sediment covers & subdues topography)

Deep ocean (avg ~5000 m)

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Deep Ocean BasinsDeep Ocean BasinsOceanic trenchesOceanic trenches

Deepest parts of the ocean (some >10,000 m)

Develop at subduction zones, parallel to volcanic arcs

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Volcanic mountains that form above mantle plumes

Example: Hawaiian Island-Emperor Seamount chain

Deep Ocean BasinsDeep Ocean Basins““Hot spots”Hot spots”

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Guyots = old, high seamounts eroded flat

Isolated volcanic peaks that may rise above sea level

Deep Ocean BasinsDeep Ocean BasinsSeamountsSeamounts

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Organisms typically prefer warm, clear, shallow water

Deep Ocean BasinsDeep Ocean BasinsCoral Reefs & AtollsCoral Reefs & Atolls

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Divergent plate boundaries (spreading centers)

Deep Ocean BasinsDeep Ocean BasinsMid-ocean RidgesMid-ocean Ridges

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Total >70,000 km long!

Deep Ocean BasinsDeep Ocean BasinsMid-ocean RidgesMid-ocean Ridges

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Rise 2-3 km above ocean basins

Deep Ocean BasinsDeep Ocean BasinsMid-ocean RidgesMid-ocean Ridges

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Normal faults & transform faults

Deep Ocean BasinsDeep Ocean BasinsMid-ocean RidgesMid-ocean Ridges

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Mostly mafic rocks (basalt & gabbro); pillow lavas

Black smokers & “weird” critters

Tube wormsBlack smokers

Deep Ocean BasinsDeep Ocean BasinsMid-ocean RidgesMid-ocean Ridges

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WWW Links in this LectureWWW Links in this Lecture

> Oceanic crust - http://en.wikipedia.org/wiki/Oceanic_crust

> Oceanic trench - http://en.wikipedia.org/wiki/Oceanic_trench

> Volcanic arc - http://en.wikipedia.org/wiki/Volcanic_arc

> Continental crust - http://en.wikipedia.org/wiki/Continental_crust

> Continental shelf - http://en.wikipedia.org/wiki/Continental_shelf

> Submarine canyon - http://en.wikipedia.org/wiki/Submarine_canyon

> Shelf-slope break - http://en.wikipedia.org/wiki/Continental_shelf#Continental_shelf_break.2C_slope.2C_and_rise

> Abyssal plain - http://en.wikipedia.org/wiki/Abyssal_plain

> Subduction zone - http://en.wikipedia.org/wiki/Subduction

> Hot spot - http://en.wikipedia.org/wiki/Hotspot_%28geology%29

> Mantle plume - http://en.wikipedia.org/wiki/Mantle_plume

> Hawaii-Emperor seamount chain -

http://en.wikipedia.org/wiki/Hawaiian-Emperor_seamount_chain

> Seamount - http://en.wikipedia.org/wiki/Seamount

> Guyout - http://en.wikipedia.org/wiki/Guyot

> Atoll - http://en.wikipedia.org/wiki/Atolls

> Mid-ocean ridges - http://en.wikipedia.org/wiki/Mid-ocean_ridges

> Pillow lava - http://en.wikipedia.org/wiki/Pillow_lava#Pillow_lava

> Black smoker - http://en.wikipedia.org/wiki/Black_smokers

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