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Stoever, Edward, C., Jr.The Rise and Fall of the Bering Land Bridge. CrustalEvolution Education Project. Teacher's Guide [and]Student Investigation.National Association of Geology Teachers.National Science Foundation, Washington, D.C.CEEP-MOD-TX20-1-8; ISBN-0-89873-052-X;ISBN-0-89873-053-879SED-75-20151; SED-77-08539; SED-78-2510423p.Ward's Natural Science Establishment, Inc., P.O. Box1712, Rochester, NY 14603 (or P.O. Box 1749,Monterey, CA 93940.)

EDRS PRICE MF01 Plus Postage. PC Not Available from EDRS.DESCRIPTORS *Earth Science; Geographic Location; *Geology;

Instructional Materials; Oceanography; Paleontology;*Science Activities; *Science Course ImprovementProjects; Science Curriculum; Science Education;Science Instruction; Secondary Education; *SecondarySchool Science; *Seismology; Teaching Guides;Teaching Methods

IDENTIFIERS *Crustal Evolution Education Project; NationalScience Foundation; *Plate Tectonics

ABSTRACTCrustal Evolution Education Project (CEEP) modules

were designed to: (1) provide students with the methods and resultsof continuing investigations into the composition, history, andprocesses of the earth's crust and the application of this knowledgeto man's activities and (2) to be used by teachers with little or noprevious background in the modern theories of sea-floor spreading,continental drift, and plate tectonics. Each module consists of twobooklets: a teacher's guide and student investigation. The teacher'sguide contains all of the information present in the studentinvestigation booklet as well as: (1) a general introduction; (2)prerequisite student background; (3) objectives; (4) list of requiredmaterials; (5) background information; (6) suggested approach; (7)

procedure, recommending one 45-minute class period for this module;(8) summary questions (with answers); (9) extension activities; and(10) list of references. Focusing on a land bridge (connectionbetween two land masses), students explain how the Bering Land Bridgefirst became possible, list two animals that migrated during each ofthe two major time periods, and explain two ways for a land bridge tobecome exposed or submerged. (Author/JN)

**A********************************************************************* Reproductions supplied by EDRS are the best that can be made *

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TheRise And Fall (;-

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THE NAHO$AL ASSOCIATION OF GEOLOGY TEACHERS

TEACHER'S GUIDECatalog No. 34W1027

For use with Student Investigation 34W1121Class dm,: two 45-ntlnuts periods

- Produced and Distributed byWard's Natural Science Eatabilshinent, Inc. Rochester, NY Monterey, CA

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4.

NAGT Crustal Evolution Education ProjectEdward C. Stoever, Jr., Project Director

Welcome to the exciting world of current researchinto the composition, history and processes of theearth's crust and the application of this knowledgeto man's activities The earth sciences arecurrently experiencing a dramatic revolution inour understanding of the way in which the earthworks CEEP modules are designed to bring intothe classroom the methods and results of thesecontinuing investigations The Crustal EvolutionEducation Project began work in 1974 underthe auspices of the National Association ofGeology Teachers CEEP materials have beendeveloped by teams of science educators,classroom teachers, and scientists Prior topublication, the materials were field tested bymore than 200 teachers and over 12,000 students

Current crustal evolution research is a breakingstory that students are living through today

About CEEP Modules ...Most CEEP modules consist of two booklets aTeacher's Guide and a Student Investigation TheTeacher's Guide contains all the informationand illustrations in the Student Investigation,plus sections printed in color, intended only for theteacher, as well as answers to the questions thatare included in tne Student InvestigationIn some modules, there are illustrations thatappear only in the Teacher's Guide, and these aredesignated by figure letters instead of the numbersequence used in the Student Investigation

For some modules, maps, rulers and othercommon classroom materials are needed, and in

The material was prepared with thesupport of National Science FoundationGrant Nos SED 75-20151, SED 77- 08533,and SED 78-25104 However, any opinions,findings conclusions, or recommendationsexpressed herein are those of the author(s)and do not necessarily reflect the viewsof NSF

In order to comply with U S Public Law94-86, every school district in the U S Ausing these materials agrees to makethem available for inspection by parents orguardians of Children engaged ineducational programs or protects of theschool district

Cowl.. 111171 by Southeast Illbsomi Noe University

Teachers and students alike have a uniqueopportunity through CEEP modules to share in theunfolding of these educationally important andexciting advances CEEP modules are designedto provide students with appealing firsthandinvestigative experiences with concepts which areat or close to the frontiers of scientific inquiry intoplate tectonics Furthermore, the CEFP modulesare designed to be used by teachers with little orno previous background in the modern theoriesof sea-floor spreading, continental drift and platetectonics

We know that you will enjoy using CEEPmodules in your classroom Read on, and beprepared to experience a renewed enthusiasm forteaching as you learn more about the living earthin this and other CEEP modules

varying quantities according to the method ofpresentation Read over the module beforescheduling its use in class and refer to the list ofMATERIALS in the module

Each module is individual and self-contained incontent, but some are divided into two or moreparts for convenience The recommended lengthof time for each module is indicated Some modulesrequire prerequisite knowledge of some aspectsof basic earth science, this is noted in theTeacher's Guide

The Rise And Fall OfThe Bering Land Bridge

INTRODUCTIONA land bridge is a connection between twolandmasses. Certain circumstances may make thebridge disappear The two landmasses are thenseparated by water. During the time whenwater lies between the masses, it is difficult foranimals to cross. When the land bridge ispresent, it is relatively easy for animals to cross

The Bering Strait separates North America fromAsia. It is a short distance. A submerged landbridge now exists where there has been dry land

PREREQUISITE STUDENT BACKGROUNDBasic knowledge of continental drift would behelpful. Specifically, students should realize thatafter the breakup of Pangaea, the North AmericanPlate moved in a generally northwesterlydirection.

A concept of animal distribution around theworld would also be useful. Students shouldrealize that animals were not always widely dis-tributed around the planet. The present locationof the Bering Strait should be pointed out to thestudents. Explain what a land bridge is andhow it may form. Also explain how the fossilrecord could show the opening and closingof the land bridge.

OBJECTIVESAfter you have completed these activities, youshould be able to1. Explain how the Bering Land Bridge firstbecame possible2. List two animals that migrated during each oftwo major time periods3. Explain two ways for a land bridge to becomeexposed or submerged

at various times in the past Scientists believethis to have been one of the most important routesfor animal migration between North Americaand Asia

The distance between the landmasses has notalways been short The drifting of the NorthAmerican Plate eventually brought the twomasses close enough for a bridge to be possibleBefore that time, no connection at this locationwas possible, because the continental masseswere separated by a wide, deep ocean

MATERIALSScissorsTape (or glue)Colored pencils or pens

4

1

BACKGROUND INFORMATIONThe Bering Land Bridge has been one of theworld's most important migration routes for about100 million years. The northwest movementand then counterclockwise rotation of the NorthAmerican Plate brought the two landmassesclose together by the end of the Cretaceous.

Throughout their existence, land animals havemoved about and migrated to new areas undervarious conditions. Three important methodsof migration across the Bering Strait are:a. Direct migration across relatively dry land.b. Filter bridge. Due to environmental stresses(in the case of the Bering area, extreme cold) someanimals pass while others cannot.

SUGGESTED APPROACH

c. "Sweepstakes" route. If areas are separatedby an obstacle, such as water in the Bering Strait,migration may take place in a lucky way,such as floating across on a log or an iceberg.

This activity has several scientific limitations.At times the existence of the bridge would dependon changes in sea level. The maps used in thisactivity depict present day coastlines. Ancientcoastlines would have been different. Also mapson Worksheets 2 and 3 do not indicate thedirection of migration since it is somewhatunclear from the fossil record.

If tape is in short supply, students may use gluefor the animal symbols. Tape should be usedfor the top edge of the maps and bridge symbolson the Worksheets so that they will flip upand down easier. (Please note: some students mayrequire an extra period to complete the map.)

The procedure is in a step-by-step format sostudents should have little trouble producing themaps on the Worksheets if they read and followthe steps carefully. After you present anynecessary background information, most studentsshould be able to work through the activitywithout help. Only at one point are they instructedto show an answer to a question to you. It wouldbe a good idea to walk around and make surethey are following instructions.

5

2

PROCEDUREPART A: Students produce El* base map thatrepresents a time before any migration, and thenplot migration patterns for the Mesozoic Era.Key word: land bridgeTime required: one 45- minute periodMaterials: scissors, tape (or glue) and coloredpencils or pens.

Carefully separate the last three pages from thisbooklet. Follow the instructions step-by-step.(Note: All of the maps on the Worksheets outlinethe continents with their present-day coastlines.Sea level has varied greatly through geologictime so it is unlikely they looked exactly like this )

Worksheet 11. After the words, Paleozoic to Mesozoic, writethe following. "Continents in motion Distancebetween too great for land bridge. No migration.Up to about 100 million years ago2. With a colored pencil, draw large arrowsto indicate the motion of North America3. With a different colored pencil, draw a smallcircle around the place in North America andthe place in Asia that will later be on either side ofthe Bering Strait

Worksheet 2This map covers the migration of some dinosaurs.It will be the most crowded of the maps. Thelines that connect similar animals need not crossthe bridge. Students should realize that fossilevidence shows each pair to be either exactlyalike, or at least very similar.

1. Separate the map on Worksheet 2 from therest of the page by cutting along the dashed lineTrim the top edge of the map along its top border

2. Carefully tape or glue only the top edge so thatit lies along the line on top of Worksheet 1

3. After the words, Late Mesozoic, write thesentence, "Migration of dinosaurs First connec-tionLate Cretaceous 100 million years ago."4. Cut out one of the three bridge symbols.

5. Tape the top edge of the bridge symbol overthe Bering Strait so that it can flip up and down

6. Now cut out dinosaur symbols a through I

6

7. Tape or glue the dinosaur symbols on thecontinents as follows

a Duckbilled - Saurolophus Asiab Duckbilled Saurolophus North Americac Giant predator Tarbosaurus Asiad Giant predator Tyrannosaurus North

Americae Armored Pinacosaurus Asiaf Armored Ankylosaurus North Americag Horned Asiah Horned North AmericaI Ostrich-like ornithomimids AsiaI Ostrich-like ornithomimids North Americak Dome-headed Pachycephalosaurus AsiaI Dome-headed Pachycephalosaurus North

America

8. Connect like animals with colored lines.

9. Look at Worksheet 2 and answer the followingHow did the dinosaurs get distributed as theyare

By walking across the strait on a land bridge.

How did scientists find evidence for thesedinosaurs?By finding fossils.

3

PROCEDURE NINrb.PART B: Students plot migration patterns forthe Cenozoic Era.Key words: noneTime required: one 45-minute periodMaterials: scissors, tape (or glue) and coloredpencils or pens.

Worksheet 3On this map of early mammal migration studentsmay want to draw their connee...Ing lines overthe land bridge.

Make sure students understand the answers tothe questions. Sea level changes in recent timeshave been due to ice ages and remelting.An ice age may lower the sea level as much as100 meters.

1. Separate Worksheet 3 from Worksheet 4 bycutting along the dashed line. Trim off thr borderat the top edge of each map.

2. Carefully tape only the top edge of Worksheet3 over the same line on which you tapedWorksheet 2

3. After the words, Early Tertiary, write "Earlymammal migration 65 million years ago."

4. Cut out animal symbols m through r.

5. Cut out one of the bridge symbols.

6. Tape the top edge of the bridge symbol overthe Bering Strait so that it matches and canbe flipped up.

7. Tape or glue the animals on the continentsas follows

m Primitive mammals multituberculatesAsia

n Primitive mammals - multituberculates -North America

o Ancestor of shrews insectivores Asiap Ancestor of shrews insectivores - North

Americaq Early hoofed mammals ungulates Asiar Early hoofed mammals ungulates North

America

8. Connect like animals with colored lines Thebridge was only usable from time to time duringthis period. (That is why you can flip the bridge!)There are two ways for the bridge to becomeusable See if you can guess what they areThe sea level may drop enough for the landbetween to become dry. The crust of the earthunder the bridge may be uplifted higher thansea level.

Check with your teacher before continuing.

4

Worksheet 4The map on Worksheet 4 shows recent migration.The direction of migration is documented sostudents only have one symbol for each animaland will draw a long arrow Instead of a connectingline.

1. Tape the top edge of Worksheet 4 alongthe same line as before.

2. Cut out the remaining map symbols After thewords, Mid-Tertiary to Present, write, "Recentmigration. 35 million years ago to modern day."

3. Cut out and tape the top edge of the remainingbridge symbol over the Bering Strait as before.

4. Tape or glue the remaining animals on thecontinents as follows*

s Horses North Americat. Camels - North Americau Bison - Asia

Elephants - Asiaw Pigs - Asiax Humans Asia

5. With colored pencils draw long arrows froms and t, making the heads of the arrows in Asia

6. Draw long arrows from u and v so the headsof the arrows are in North America

7. Under Pig write, "No migration throughstrait," which means that the pigs did not migratethrough the Bering Strait

8. Draw an arrow from the human in Asia acrossthe Bering Strait with the head of the arrowin North America

9. Below this line write the words, "about 15,000years ago" Scientists are more certain of theorigin and migration patterns of the animals onthis map, than of the kinds shown on yourother maps

Now you have a finished map of the migration ofanimals across the Bering Land Bridge aftercontinental drift brought the continents closetogether

"1I

SUMMARY QUESTIONS1. What prevented the Bering Land Bridge frombeing used before the Cretaceous?There was a deep ocean between them. Theplates had not drifted doss enough.

2. List two dinosaurs (common or scientificnames) that migrated during the Cretaceous.Duckbilled (Saurolophus), giant predator(TarbosaurusTyrannosaurus), armored (Pinaco-saurusAnkylosaurus), homed, ostrich-like(omithomimids), dome-headed (Pachycephalo-saurus).

3. List two early mammals that migrated.Primitive mammals (multituberculates), ancestorof shrews (insectivores), early hoofed mammals(ungulates).

4. List two recent animals that migratedHorses, camels, bison, elephants, humans.

S. Why did you construct the bridge to flip up?Because the bridge can only be used from timeto time.

S. Explain how a land bridge can disappearThe sea level rises or the crust of the earthunder the bridge subsides.

EXTENSION I

If you want your map to be complete, write outan appropriate key to the animal symbols on themap and tape it along the same line on whichyou taped Worksheets 2, 3 and 4 on 1.

REFERENCE

Colbert, E.H , 1976, Fossils and the driftingcontinents Fossils Magazine, v 1, no. 1, p. 5-22

S

Continental Droll and the Migration of Animals Across the Bering Land Bridge

Answer Sheet 1 (PART A)Paleozoic to Mesozoic

Continents in motion Distance between to great for and bridgeNo migration Up to about 100 million years ago

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Answer Sheet 2 (PART A)

Late MesozoicMigration of dinosaurs First connection Late Cretaceous 100m Ilion years ago

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Answer Sheet 4 (PART B)Mid-Tertiary to PresentRecent migration 35 million years ago to modern day

1.2

NAGT Crustal EvolutionEducation Project ModulesCEEP Modules are listed here in alphabeticalorder. Each Module is designed for use inthe number of class periods indicated Forsuggested sequences of CEEP Modules tocover specific topics and for correlationof CEEP Modules to standard earth sciencetextbooks, consult Ward's descriptiveliterature on CEEP The Catalog Numbersshown here refer to the CLASS PACKof each Module consisting of a Teacher'sGuide and 30 copies of the StudentInvestigation See Ward's descriptiveliterature for alternate order quantities

Copyright 1979 Except for the rights tomaterials reserved by others thepublisher and the Copyright owner herebygrant permission without charge todomestic persons of the U S and Canadafor use of this Work and related materialsin the English language in the U S andCanada after 1985 For conditions of useand permission to use the Work or any partthereof for foreign publications orPublications in other than the Englishlanguage apply to the Copyright owner orpublisher

13

CEEP ModuleClass CLASS PACK

Periods Catalog No.

A Sea-floor Mystery: Mapping 3 34 W 1201Polarity Reversals

Continents And Ocean Basins: 3-5 34 W 1202Floaters And Sinkers

Crustal Movement: A Major Forcein Evolution

2-3 34 W 1203

Deep Sea Trenches And Radioactive 1 34 W 1204Waste

Drifting Continents And Magnetic 3 34 W 1205Fields

Drifting Continents And Wandering 4 34 W 1206Poles

Earthquakes And Plate 2 34 W 1207Boundaries

Fossils As Clues To Ancient 2-3 34 W 1208Continents

Hot Spots In The Earth's Crust 3 34 W 1209How Do Continents Split Apart? 2 34 W 1210How Do Scientists Decide Which is 2 34 W 1211

The Better Theory?How Does Heat Flow Vary In The 2 34 W 1212

Ocean Floor?How Fast Is The Ocean Floor 2-3 34 W 1213

Moving?Iceland: The Case Of The Splitting 3 34 W 1214

PersonalityImaginary Continents: A Geological 2 34 W 1215

PuzzleIntroduction To Lithospheric 1-2 34 W 1216

Plate BoundariesLithospheric Plates And Ocean 2 34 W 1217

Basin TopographyLocating Active Plate Boundaries 2-3 34 W 1218

By Earthquake DataMeasuring Continental Drift: The 2 34 W 1219

Laser Ranging ExperimentMicrofossils, Sediments And 4 34 W 1220

Sea-floor SpreadingMovement Of The Pacific Ocean 2 34 W 1221

FloorPlate Boundaries And Earthquake 2 34 W 1222

PredictionsPlotting The Shape Of The Ocean 2-3 34 W 1223

FloorGuake Estate (boar ii..,:robl 3 34 W 1224Spreading Sea Floors And Fractured 2 34 W 1225

RidgesThe Rise And Fall Of The Bering 2 34 W 1227

Land BridgeTropics in Antarctica? 2 34 W 1228Volcanoes: Where And Why? 2 34 W 1229What Happens When Continents 2 34 W 1230

Collide?When A Piece Of A Continent 2 34 W 1231

Breaks OffWhich Way is North? 3 34 W 1232Why Doss Sea Level Change? 2-3 34 W 1233

a

111111111 .Wares Natural Science Establishment, Inc.P.O. Sox 1712, Rochester, New York 14603 P.O. Box 1749 Monterey, California 93940

CUP MOM 1110. 11011 141 1.4OM 11411111$41104 hinted W n Man.

(

CRUSTALEVOLUTIONEDUCATION

PROJECT

NAME DATE

Student InvestigationCatalog No 34W1127

The Rise And FallOf The Bering Land Bridge

INTRODUCTION whimasamarmagramissimeitiwroso..../.2.4.

A land bridge is a connection between twolandmasses Certain circumstances may make thebridge disappear The two landmasses are thenseparated by water During the time whenwater lies between the masses, it is difficult foranimals to cross When the land bridge ispresent, it is relatively easy for animals to cross

The Bering Strait separates North America fromAsia It is a short distance A submerged landbridge now exists where there has been dry landat various times in the past Scientists believethis to have been one of the most important routesfor animal migration between North Americaand Asia

The distance between the landmasses has notalways been short The drifting of the NorthAmerican Plate eventually brought the twomasses close enough for a bridge to be possibleBefore that time, no connection at this locationwas possible, because the continental masseswere separated by a wide, deep ocean

OBJECT IVES

After you have completed these activities, youshould be able to1. Explain how the Bering Land E ,dge firstbecame possible2. List two animals that migrated during each oftwo major time periods3. Explain two ways for a land bridge to becomeexposed or submerged

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PROCEDUREPART AMaterials scissors, tape (or glue) and coloredpencils or pens

Carefully separate the last three pages from thisbooklet Follow the instructions step-by-step(Note: All of the maps on the Worksheets outlinethe continents with their present-day coastlines.Sea level has varied greatly through geologictime so it is unlikely they looked exactly like this )

Worksheet 11. After the words, Paleozoic to Mesozoic, writethe following "Continents in motion Distancebetween too great for land bridge No migrationUp to about 100 million years ago."2. With a colored pencil, draw large arrowsto indicate the motion of North America.3. With a different colored pencil, draw a smallcircle around the place in North America andthe place in Asia that will later be on either side ofthe Bering Strait

2

Worksheet 21. Separate the map on Worksheet 2 from therest of the page by cutting along the dashed line.Trim the top edge of the map along its top border.

2. Carefully tape or glue only the top edge so thatIt lies along the line on top of Worksheet 1

3. After the words, Late Mesozoic, write thesentence, "Migration of dinosaurs First connec-tionLate Cretaceous 100 million years ago4. Cut out one of the three bridge symbols

5. Tape the top edge of the bridge symbol overthe Bering Strait so that it can flip up and down

6. Now cut out dinosaur symbols a through I.

7. Tape or glue the dinosaur symbols on thecontinents as follows

a Duckbilled Saurolophus Asiab Duckbilled Saurolophus North Americac Giant predator Tarbosaurus Asiad Giant predator Tyrannosaurus North

Americae Armored - Pinacosaurus Asiaf Armored Ankylosaurus North Americag Horned Asiah Horned North Americat Ostrich-like ornithomimids AsiaI Ostrich-like ornithomimids North Americak Dome-headed - Pachycephalosaurus - AsiaI Dome-headed Pachycephalosaurus North

America

8. Connect like animals with colored lines

9. Look at Worksheet 2 and answer the followingHow did the dinosaurs get distributed as theyare?

How did scientists find evidence for thesedinosaurs?

PROCEDURE 11PART BMaterials* scissors, tape (or glue) and coloredpencils or pens

Worksheet 3

1. Separate Worksheet 3 from Worksheet 4 bycutting along the dashed line Trim off the borderat the top edge of each map

2. Carefully tape only the top edge of Worksheet3 over the same Itne on which you tapedWorksheet 2

3. After the words, Early Tertiary, write "Earlymammal migration 65 million years ago

4. Cut out animal symbols m through r

5. Cut out one of the bridge symbols

6. Tape the top edge of the bridge symbol overthe Bering Strait so that it matches and canbe flipped up

7. Tape or glue the animals on the continentsas follows

m Primitive mammalsAsia

n Primitive mammalsNorth America

o Ancestor of shrewsp Ancestor of shrews

Americaq Early hoofedr Early hoofed

America

8. Connect like animals with colored lines Thebridge was only usable from time to time duringthis period (That is why you can flip the bridge!)There are two ways for the bridge to becomeusable See if you can guess what they are

multituberculates

multituberculates

insectivores Asiainsectivores North

mammals ungulates Asiamammals ungulates North

Check with your teacher before continuing

:7

3

Works Mit 4

1. Tape the top edge of Worksheet 4 alongthe same line as before

2. Cut out the remaining map symbols. After thewords, Mid-Tertiary to Present, write, "Recentmigration 35 million years ago to modern day

3. Cut out and tape the top edge of the remainingbridge symbol over the Bering Strait as before

4. Tape or glue the remaining animals on thecontinents as follows.

s Horses - North Americat Camels North Americau Bson Asiav Elephants Asiaw. Pigs Asiax. Humans Asia

S. With colored pencils draw long arrows froms and t, making the heads of the arrows in Asia

6. Draw long arrows from u and v so the headsof the arrows are in North America

7. Under Ptg write, "No migration throughstrait," which means that the pigs did not migratethough the Bering Strait8. Draw an arrow from the human in Asia acrossthe Bering Strait with the head of the arrowin North America

9. Below this line write the words, "about 15,000years ago" Scientists are more certain of theorigin and migration patterns of the animals onthis map, than of the kinds shown on yourcther maps

Now you have a f nished map of the migration ofanimals across the Bering Land Bridge aftercontinental drift brought the continents closetogether

4

1 8

SUMMARY QUESTIONS1. What prevented the Bering Land Bridge frombeing used before the Cretaceous?

2. List two dinosaurs (common or scientificnames) that migrated during the Cretaceous

3. List two early mammals that migrated

EXTENSION

4. List two recent animals that migrated

5. Why did you construct the bridge to flip up?

6. Explain how a land bridge can disappear

If you want your map to be complete, write outan appropriate key to the animal symbols on themap and tape it along the same line on whichyou taped Worksheets 2, 3 and 4 on 1.

1y5

Continental Drift and the Migration of Animals Across the Bering Land Bridge

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Worksheet 3 (PART B)Early Tertiary

Worksheet 4 (PART B)Mid-Tertiary to Present