ESS INTRO

•Describe evidencefor the mechanismbehind continentaldrift.

1.Describe 1 evidencefor continental driftAND how itsupports the theory.

2.Why was the theoryof continental driftnot accepted rightaway?

02/05/2015

Continental Drift

•All continents were part of a giantlandmass called Pangaea thatexisted 200 million years ago.

continental drift

continental drift

continental drift

continental drift

Wegener’s Evidence forContinental Drift

1.Continents fit together like apuzzle.

2.Fossil correlation

3.Mountain ranges / Rocklayers line up

4.Glacier evidence

1. Continents fit together like apuzzle.

2. Fossil Correlation

•Same fossilfound ondifferentcontinents

•How did thefossils getfromcontinent tocontinent?

http://upload.wikimedia.org/wikipedia/commons/thumb/2/22/Snider-Pellegrini_Wegener_fossil_map.gif/500px-Snider-Pellegrini_Wegener_fossil_map.gif

3. Mountain Ranges and RockLayers line up

4. Glacier Evidence

•Glacier residuepresent in warmclimatecontinents.

•This suggeststhat thecontinents musthave moved froma differentlatitude.

So why was Wegener’s theorynot accepted at first?

•No mechanism for movingcontinents.

–i.e. How do the continentsmove?

Harry Hess

•US geologist andNaval officer (1940s)

•Gathered moreevidence to supportthe theory ofcontinental drift.

Hess’ Evidence

1.Ocean Topography

2.Seafloor Magnetism

3.Seafloor Age

What does the ocean floorlook like?

•Page 451

–Read and define…

•Abyssal Plain

•Deep-sea Trench

•Mid-ocean Ridge

•Page 474

–Read and take notes

•Ocean-floor Topography

Ocean Floor Topography

Is the Ocean Floor flat?

NO

Ocean Floor Topography

http://upload.wikimedia.org/wikipedia/commons/thumb/1/13/Oceanic_basin.svg/800px-Oceanic_basin.svg.png

Abyssal Plains

•Flat plains of sediments

http://farm6.staticflickr.com/5024/5601522583_90f594ceca_z.jpg

Deep Sea Trenches

•Elongated depressions

•Deepest parts of the ocean

http://t0.gstatic.com/images?q=tbn:ANd9GcSNoSysv96Br9KzkD2El_KnopKaJH8WDWT_X3RiRf0OUfa8_yQE

$C:\Users\owner\Desktop\mariana-trench-graphic-30812.jpg$

http://cdn.lightgalleries.net/4bd5ebf883187/images/Ocean-Slot-Canyon_4158-3.jpg

Mid-Ocean Ridges

•Underwater mountain ranges

http://oceansjsu.com/images/SEPR.jpg

http://2.bp.blogspot.com/-p5m3GK89G90/Tc6uEsclCvI/AAAAAAAACQU/M_OsxdquHY8/s1600/A-diver-swims-between-the-003.jpg

A scuba diver between the Eurasian and North American Plates

http://www.michaelmasser.co.uk/Travel/Iceland/i-ZhBpFtj/0/L/Mid-Atlantic-Ridge-Iceland-HDR-L.jpg

Ocean Floor Topography

How did thesefeatures form?

Magnetism

•Lava contains iron

–Iron is magnetic (points tomagnetic north)

•When the lava solidifies, the ironwill be “frozen” in the direction ofthe magnetic north at the time oferuption.

Diverging ridge magnetism.gif (32515 bytes)

http://oceansjsu.com/images/exp5_mag_field_flip.gif

http://oceansjsu.com/images/exp5_mag_field_flip.gif

http://oceansjsu.com/images/exp5_mag_field_flip.gif

Magnetism

•Direction of the iron at theseafloor is not always the same.

•The patterns are mirror imageson either side of the ridges.

magrev

Age of the Seafloor

http://www.ifremer.fr/serpentine/fiches/fiche14-img2-web.jpg

Age of the Seafloor

•Seafloor rocks have different ages.

•Similar pattern of age on either sideof the ridges.

•Youngest rocks towards the centerof the ocean (by the ridges)

•Oldest rocks closest to thecontinents