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1 THE BLUE PLANET: THE WORLD’S OCEANSOrigin of Sea and Sky ■The Universal Sea ■The Iapetus Sea ■ The Panthalassa Sea ■The Tethys Sea ■The Atlantic 1 2 MARINE EXPLORATION: DISCOVERIES ON

Marine Geology

MARINE GEOLOGY

Exploring the New Frontiers of the Ocean, Revised Edition

Copyright © 2003, 1996 by Jon Erickson

All rights reserved No part of this book may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, or by any information storage or retrieval systems, without permission in writing from the publisher For information contact:

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Library of Congress Cataloging-in-Publication Data

Erickson, Jon, 1948–

Marine geology: exploring the new frontiers of the ocean/Jon Erickson.—Rev ed.

p cm.—(The living earth)

Includes bibliographical references and index.

ISBN 0-8160-4874-6 (hardcover: alk paper)

1 Submarine geology 2 Marine biology I.Title.

QE39 E68 2003

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1 THE BLUE PLANET: THE WORLD’S OCEANS

Origin of Sea and Sky ■The Universal Sea ■The Iapetus Sea ■

The Panthalassa Sea ■The Tethys Sea ■The Atlantic 1

2 MARINE EXPLORATION: DISCOVERIES

ON THE SEABED

Exploring the Ocean Floor ■Surveying the Seabed ■

Geologic Observations ■Ocean Drilling ■Magnetic Surveys ■

Satellite Mapping 31

3 THE DYNAMIC SEAFLOOR: THE OCEANIC CRUST

Lithospheric Plates ■Oceanic Crust ■The Rock Cycle ■

Ocean Basins ■Submarine Canyons ■Microplates and Terranes 60

4 RIDGES AND TRENCHES: UNDERSEA MOUNTAINSAND CHASMS

The Midocean Ridges ■The Heat Engine ■Seafloor Spreading ■

Basaltic Magma ■The Circum-Pacific Belt ■

The Deep-Sea Trenches ■ Plate Subduction 87

5 SUBMARINE VOLCANOES: Eruptions

ON THE OCEAN FLOOR

The Ring of Fire ■The Rising Magma ■Island Arcs ■

Guyots and Seamounts ■Rift Volcanoes ■Hot-Spot Volcanoes ■

Volcanic Activity 114

6 ABYSSAL CURRENTS: OCEAN CIRCULATION

Rivers in the Abyss ■El Niño ■Abyssal Storms ■Tidal Currents ■

Ocean Waves ■Seismic Sea Waves 145

7 COASTAL GEOLOGY: THE ACTIVE COASTLINE

Sedimentation ■Storm Surges ■Coastal Erosion ■Wave Impacts ■

Coastal Subsidence ■Marine Transgression 172

8 SEA RICHES: RESOURCES OF THE OCEAN

Law of the Sea ■Oil and Gas ■Mineral Deposits ■

Energy from the Sea ■Harvesting the Sea 201

9 MARINE BIOLOGY: LIFE IN THE OCEAN

Biologic Diversity ■Marine Species ■ Life in the Abyss ■

Coral Reefs ■The Vent Creatures ■The Intertidal Zone 229

10 RARE SEAFLOOR FORMATIONS: UNUSUAL GEOLOGY

ON THE SEABED

Mud Volcanoes ■Subsea Geysers ■Submarine Slides ■

Sea Caves ■Seafloor Craters ■Undersea Explosions 257Conclusion 285Glossary 286Bibliography 297

1 The Geologic Time Scale 2

2 Radiation and Extinction of Species 10

3 Evolution of the Biosphere 12

4 The Major Ice Ages 13

5 Continental Drift 47

6 Comparison of Magnetic Reversals with Other Phenomena 56

7 Classification of the Earth’s Crust 66

8 The Amount of Carbon Relative to Life 72

9 History of the Deep Circulation of the Ocean 76

10 The World’s Ocean Trenches 107

11 Comparison of Types of Volcanism 115

12 Major Volcanic Disasters of the 20th Century 118

13 Classification of Volcanic Rocks 121

14 Major Tidal Bores 163

15 The Beaufort Wind Scale 179

tableS

16 Major Changes in Sea Level 194

17 Natural Resource Levels 202

18 Productivity of the Oceans 226

19 Classification of Species 235

T he author thanks the National Aeronautics and Space Administration

(NASA), the National Oceanic and Atmospheric Administration

(NOAA), the U.S Army Corps of Engineers, the U.S Department of

Agriculture-Forest Service, the U.S Department of Agriculture-Soil

Conser-vation Service, the U.S Defense Nuclear Agency, the U.S Department of

Energy, the U.S Geological Survey (USGS), the U.S Maritime

Administra-tion, the U.S Navy, and the Woods Hole Oceanographic Institution (WHOI)

for providing photographs for this book

The author thanks Frank K Darmstadt, Senior Editor, and the rest of the

Facts On File staff for their invaluable contributions to the making of this book

acknowledgments

Oceans cover approximately two-thirds of the Earth’s surface, yet we

have explored less of the ocean’s depths and mysteries than the

sur-faces of several nearby planets The oceans have inspired myths and

legends and have been the sources of intrigue, fear, and hope for thousands of

years They have hindered migration of peoples and biota between distant

continents yet paradoxically now serve as a principal means of transportation

Oceans provide us with incredible mineral wealth and renewable food and

energy sources yet also breed devastating hurricanes Life on Earth may have

begun in environments around hot volcanic events on the seafloor, and we are

only beginning today to explore the diverse and unique fauna that thrive in

deep, dark waters around similar vents

In the revised edition of Marine Geology, Jon Erickson explores several

ideas hypothesizing the origin of the Earth, continents, and oceans and how

these processes fit into the origin of the universe.The role of oceans and water

in the development of plate tectonics is discussed in detail, while the reader is

given essential information on how plate tectonics works Ocean basins have

continually expanded and contracted on Earth, and the continents have

alter-nately converged into large single supercontinents and then broken apart by

the formation of new ocean basins.The appearance, evolution, and extinction

of different life-forms are inextricably linked to the expansion and

contrac-tion of ocean basins, partly through the changing environmental condicontrac-tions

associated with tectonic processes.The history of several different ocean basins

over the past billion years is discussed in Marine Geology, as well as the

chang-ing life-forms in each successive ocean basin

foreword

Erickson presents a fascinating history of ocean exploration He showshow early explorations were slowly able to reveal data about ocean currentsand routes to distant lands and how some dredging operations uncoveredhuge deposits of metals on the seafloor.Tremendous leaps in our understand-ing of the structure and topography of the seafloor were acquired during sur-veying for the navigation of submarines and detecting enemy submarinesduring World War II Magnetometers towed behind ships, and accurate depthsoundings provided data that led to the formulation of the hypothesis ofseafloor spreading, adding the oceanic counterpart to the idea of continentaldrift.Together these two theories became united as the plate tectonic revolu-tion This sets the stage for succeeding chapters on the mid-ocean ridges,deep-sea trenches, and submarine volcanoes.

Ocean circulation is responsible for much of the world’s climate Mildfoggy winters in London are caused by warm waters from the Gulf of Mex-ico flowing across the Atlantic in the Gulf Stream to the coast of the BritishIsles Large variations in ocean and atmospheric circulation patterns in thePacific lead to alternating wet and dry climate conditions known as El Niñoand La Niña.These variations affect Pacific regions most strongly but are feltthroughout the world

Other movements of water are more dramatic, including the sometimesdevastating tsunami that may be initiated by earthquakes, volcanic eruptions, andgiant submarine landslides One of the most tragic tsunami in recent history wasgenerated by the eruption of the Indonesian volcano Krakatau [Krakatoa] in1883.When Krakatau erupted, it blasted out a large part of the center of the vol-cano, and seawater rushed in to fill the hole This seawater was immediatelyheated, and it exploded outward in a steam eruption and a huge wave of hotwater The tsunami generated by this eruption reached more than 120 feet inheight and killed an estimated 36,500 people in nearby coastal regions In 1998

a catastrophic 50-foot-high wave unexpectedly struck Papua New Guinea,killing more than 2,000 people and leaving more than 10,000 homeless.The oceans are full of rich mineral deposits, including oil and gas on thecontinental shelves and slopes and metalliferous deposits formed near mid-ocean ridge vents Much of the world’s wealth of manganese, copper, and goldlies on the seafloor The oceans also yield rich harvests of fish, and care must

be taken that we do not deplete this source by overfishing Sea vegetables aregrowing in popularity and their use may help alleviate the increasing demandfor space in fertile farmland.The oceans offer the world a solution to increas-ing energy and food demands in the face of a growing world population Newlife-forms are constantly being discovered in the ocean’s depths, and under-standing these creatures is necessary before any changes we make to theirenvironment causes them to perish forever

— Timothy M Kusky, Ph.D

T his planet contains so much water that perhaps it should have been

better named Oceania It is the only known body in the solar system

that is surrounded by water filled with unique geologic structures and

teeming with a staggering assortment of marine life Some of the strangest

creatures on Earth, whose ancestors go back several hundred million years, live

on the deep ocean floor Many undersea ridges host an eerie world that time

forgot—a cold, dark abyss consisting of tall chimneys spewing hot,

mineral-rich water that supports unusual species previously unknown to science

The floor of the ocean presents a rugged landscape unmatched

any-where on the continents Vast undersea mountain ranges much more

exten-sive than those on land crisscross the seabed Although deeply submerged, the

midocean ridges are easily the most prominent features on the planet The

ocean floor is continuously being created at spreading ridges, where molten

rock oozes out of the mantle, and destroyed in the deepest trenches of the

world Much of the world’s untapped wealth lies undersea.The seabed

there-fore offers new frontiers for future exploration of mineral resources

An extraordinary number of volcanoes are hidden under the waves,

many more than on the land Most of the volcanic activity that continually

remakes the surface of Earth occurs on the ocean floor Active volcanoes

ris-ing up from the bottom of the ocean create the tallest mountains Most of the

world’s islands in fact began as undersea volcanoes that broke the surface of

the sea However, the preponderance of marine volcanoes is not exposed at

the surface but spread out on the ocean floor as isolated seamounts

INTRODUCTION

Chasms that challenge the largest terrestrial canyons plunge to greatdepths Massive submarine slides gouge deep depressions into the seabed anddeposit enormous heaps of sediment onto the ocean floor Undersea slidesalso occasionally generate tall waves that pound nearby shores, causing muchdestruction to seaside communities.Abyssal storms with strong currents sculptthe ocean bottom, churning up huge clouds of sediment and dramaticallymodifying the seafloor The scouring of the seabed and deposition of largeamounts of sediment result in a highly complex marine geology.

This revised and updated edition is a much expanded and more sive examination of the intriguing subject of marine geology Science enthu-siasts will particularly enjoy this fascinating subject and gain a betterunderstanding of how the forces of nature operate on Earth Students of geol-ogy and Earth science will also find this a valuable reference book to furthertheir studies Readers will enjoy this clear and easily readable text that is wellillustrated with extraordinary photographs, detailed illustrations, and helpfultables A comprehensive glossary is provided to define difficult terms, and abibliography lists references for further reading The geologic processes thatshape the surface of this planet are an example of the spectacular forces thatcreate the living Earth

inclu-This opening chapter chronicles the formation of Earth and the

evolu-tion of the oceans Earth is unique among planets, because it is the

only body in the solar system with a water ocean and an oxygen

atmosphere As many as 20 oceans have come and gone throughout this

planet’s long history (Table 1) as continents drifted apart from each other and

reconverged into supercontinents.The present oceans formed when a

super-continent named Pangaea, Greek for “all lands,” broke apart into today’s

con-tinents about 170 million years ago

Prior to the breakup of Pangaea, a single large ocean called Panthalassa,

Greek for “universal sea,” surrounded the supercontinent Before the

assem-blage of Pangaea, all continents surrounded an ancient Atlantic Ocean called

the Iapetus Sea Deeper into the past, the continents again formed a

super-continent named Rodinia, Russian for “Motherland.” Its breakup created

entirely new seas, which participated in life’s greatest explosion of new

species Life itself possibly evolved at the bottom of a global ocean not long

after Earth’s creation

1

The Blue Planet

The World’s Oceans

1

Age (millions First Era Period Epoch of years) Life-forms Geology

Holocene 0.01Quaternary

Pleistocene 3 Humans Ice ageCenozoic Pliocene 11 Mastodons Cascades

NeogeneMiocene 26 Saber-toothed tigers AlpsTertiary Oligocene 37

PaleogeneEocene 54 WhalesPaleocene 65 Horses, Alligators Rockies

Cretaceous 135

Birds Sierra NevadaMesozoic Jurassic 210 Mammals Atlantic

DinosaursTriassic 250

Permian 280 Reptiles AppalachiansPennsylvanian 310 Ice age

TreesCarboniferous

Paleozoic Mississippian 345 Amphibians Pangaea

InsectsDevonian 400 SharksSilurian 435 Land plants LaursiaOrdovician 500 Fish

Cambrian 570 Sea plants Gondwana

Shelled animals

700 InvertebratesProterozoic 2500 Metazoans

3500 Earliest lifeArchean 4000 Oldest rocks

4600 Meteorites

ORIGIN OF SEA AND SKY

An incredible amount of water resides in the solar system, much more than

on Earth alone As the Sun emerged from gas and dust, tiny bits of ice and

rock debris gathered in a frigid, flattened disk of planetesimals surrounding the

infant star.The temperatures in some parts of the disk might have been warm

enough for liquid water to exist on the first solid bodies to form In addition,

water vapor in the primordial atmospheres of the inner terrestrial planets

might have been eroded away by planetesimal bombardment and blown

beyond Mars by the strong solar wind of the infant Sun Once planted in the

far reaches of the solar system, ice crystals coalesced into comets that returned

to Earth to supply it with additional water

The creation of the Moon (Fig 1) remains a mystery Perhaps a Mars-sized

body slammed into Earth and splashed enough material into orbit to coalesce

into a daughter planet.The presence of a rather large moon, the biggest of any

moon in the solar system in relation to its mother planet, might have had a

major influence on the initiation of life The unique properties of the

Earth-Moon system raised tides in the ocean Cycles of wetting and drying in tidal

pools might have helped the planet acquire life much earlier than previously

thought possible.The Moon might also have been responsible for the relatively

Figure 1 The surface of the Moon viewed from an

Apollo spacecraft showing

many of its terrain features.

(Photo courtesy NASA)

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