name supers
Sridhar Anandakrishnan
Geologist, University of Alabama
Nelia Dunbar
Geologist, NM Inst. of Mining and Technology
Bill McIntosh
Geologist, NM Inst. of Mining and Technology
David Harwood
Micropaleontologist, University of Nebraska, Lincoln
David Marchant
Geomorphologist, Boston University
***
ANTARCTICA IS A CONTINENT 98% COVERED IN ICE...
BUT HAS IT ALWAYS BEEN A FROZEN, LIFE-LESS DESERT?
AND IF IT WAS ONCE MUCH WARMER, COULD THE ICE MELT AGAIN AND MAKE GLOBAL SEA LEVELS RISE?
IN THIS VIDEO WE'LL SEE HOW ONE RESEARCH TEAM USES EXPLOSIVES TO TRACK HUGE AMOUNTS ON ICE ON THE MOVE!
title FIRE DOWN BELOW
WE'LL EXPLORE EARTH'S SOUTHERN-MOST ACTIVE VOLCANO, AND THE FORCES WHICH SHAPE IT...
AND WE'LL HEAR HOW SCIENTISTS "READING THE ROCKS" COME TO VERY DIFFERENT CONCLUSIONS ABOUT THE PAST AND FUTURE OF THIS CONTINENT.
***
titles
PASSPORT TO ANTARCTICA
program 2
Fire and Ice
***
title: "Ice in Motion"
WHAT WE SEE ON ANY DAY IN ANTARCTICA IS JUST A SNAPSHOT OF A CONTINENT IN MOTION.
SOME CHANGES ARE SLOW, ABOUT THE SAME SPEED THAT YOUR FINGERNAILS GROW!
OTHERS, LIKE THIS GLACIER CALVING, ARE MUCH FASTER.
SCIENTISTS ARE TRYING TO UNDERSTAND WHAT THESE MOTIONS MEAN FOR THE PAST AND FUTURE OF OUR PLANET.
AT THE SOUTH POLE, FOR EXAMPLE, THE ENTIRE ICE SHEET IS SLIPPING OVER THE UNDERLYING SURFACE AT 10 METERS PER YEAR.
THAT'S WHY, EACH YEAR, THE NATIONAL SCIENCE FOUNDATION HAS TO RELOCATE THE MARKER FOR THE EXACT GEOGRAPHIC SOUTH POLE, 90 DEGREES SOUTH LATITUDE.
BUT AS YOU LOOK OVER THE ENTIRE CONTINENT, THERE ARE SOME PLACES WHERE HUGE RIVERS OF ICE FLOW MUCH MORE RAPIDLY DOWN FROM THE POLE TO THE SHORE.
THAT'S WHY SRIDHAR ANANDAKRISHAN FROM THE UNIVERSITY OF ALABAMA IS OUT HERE IN THE MIDDLE OF CENTRAL WEST ANTARCTIC.
HE'S PART OF A FIELD PROGRAM TRYING TO DISCOVER WHY SOME "ICE STREAMS" MOVE SO MUCH FASTER THAN THE SLOW CREEP OF THE REST OF THE ICE.
name title: Sridhar Anandakrishnan
Geologist, University of Alabama
Sridhar
We're in the middle of the West Antarctic ice sheet. We're pretty close to the South Pole, but more importantly than that, we're sitting on a mile of ice. In every direction, for a thousand miles in every direction, it's just ice, which is an enormous amount of ice. There's no other place on Earth which has this much ice, that just stays year round, it never melts. It never goes anywhere.
SRIDHAR'S RESEARCH PROGRAM INVOLVES SETTING OFF CAREFULLY-CONTROLLED EXPLOSIVE CHARGES, WHICH SEND SEISMIC WAVES DOWN THROUGH THE ICE, BOUNCING BACK UP TO SETS OF COMPUTERIZED DETECTORS.
BY MEASURING HOW LONG IT TAKES TO GET AN ECHO BACK FROM THE UNDERLYING ROCK-ICE BOUNDARY, SRIDHAR'S TEAM CAN TELL A LOT ABOUT THE ICE, WHAT KIND OF ROCK IT SITS ON, AND HOW FAST IT'S MOVING.
Sridhar:
The question that I'm trying to look at is, is this ice sheet that we're on, that's been here for so long, is it possibly something that might be affected by some of the things that Man is doing to his environment. By what you've all heard about, global warming, and those sorts of effects that we have on the environment, can that affect something as enormous as this ice sheet?
RUNNING THE EXPERIMENT TAKES BUILDING A SMALL TOWN OUT ON THE ICE.
THERE ARE JAMESWAY TENTS... GOOD FOOD... LOTS OF SKIDOOS... TRACTORS... A COMPUTER LAB. UNDER CANVAS.
AHEAD OF THE EXPERIMENTERS THERE'S A TEAM OF POLAR ICE CORERS WHO DRILL DEEP HOLES FOR THE EXPLOSIVE CHARGES.
THEN THE RESEARCHERS CAN GET TO WORK.
SRIDHAR THINKS THERE MUST BE SOMETHING SPECIAL ABOUT THE ROCKS HERE IN PARTS OF WEST ANTARCTICA THAT MAKES IT EASY FOR HUGE AMOUNTS OF ICE TO SLIDE RAPIDLY ACROSS THE BEDROCK.
Sridar
Just a few tens of miles, maybe a hundred miles to the west of us are what are called the ice streams. These are very fast flowing glaciers, basically. They're very unusual because they flow, for a glacier at an enormous rate of maybe 2000 feet per year, which is an enormous amount for a glacier. And we'd like to know what's different about the bed, why didn't the ice stream start here or up that way? A few more hundred miles to the east, why did it start where they do start? Is it something about the rock, is it because the rock changes and so the ice can flow more easily and so the ice streams form. Or is it some other reason?
HIS HUNCH IS THAT WHERE THE ROCKS ARE SOFT, THE ICE SLIDES EASILY... BUT WHERE IT'S HARD, THE ICE STREAMS SLOW DOWN.
Sridhar
How fast the ice moves across those rocks is determined by the type of rock, and we have no idea, we have no way of knowing what that type is, because it's a mile down and we can't just go down to it and pick up a piece and look at it. So we have to use indirect methods.
THE WEST ANTARCTIC ICE SHEET IS CERTAINLY REMOTE FROM NORTH AMERICA-BUT THE RESULTS OF ANY MELTING COULD BE FELT AROUND THE GLOBE.
Sridhar:
Sea level would rise by up to twenty feet, something like that ...if the water were to go up just twenty feet, it would actually go inland quite a long way.
RECENTLY SRIDHAR HAS BEEN ADDING A NETWORK OF PASSIVE SEISMIC DETECTORS TO HIS "EXPLOSIONS".
BY WIRING ANTARCTICA AND SEEING DOWN THROUGH MILES OF ICE, WE MAY BE ABLE TO BUILD AN EARLY WARNING SYSTEM TO GAUGE THE SHAPE OF THINGS TO COME.
SOME DEGREE OF CHANGE IS NATURAL, AND INEVITABLE.
AS WE'VE SEEN, ON GEOLOGICAL TIME SCALES, ANTARCTICA-AND ALL THE OTHER CONTINENTS-ARE IN MOTION, DRIVEN ULTIMATELY BY "FIRE DOWN BELOW."
GEOLOGISTS NOW BELIEVE EARTH HAS A CORE WITH A TEMPERATURE OF AROUND 5,000 DEGREES CENTIGRADE.
IN SOME PLACES, THE HEAT MELTS THE ROCKS OF EARTH'S MANTLE, AND SPOUTS IT UP AND OUT THROUGH THE CRUST IN A VOLCANO.
THIS IS MOUNT EREBUS, ABOUT 20 MILES AWAY FROM McMURDO STATION, EARTH'S MOST SOUTHERLY ACTIVE VOLCANO...
name title: Nelia Dunbar
Geologist, NM Inst. of Mining and Technology
Nelia Dunbar:
Right now we're at the summit of Mt. Erebus, which is about 13,000 feet high. It's a very unique volcano for many reasons. The main one is, down in that pit is a lava lake.
VOLCANOES HAVE BEEN AN IMPORTANT SOURCE OF THE GASES THAT FORM EARTH'S ATMOSPHERE.
Nelia:
As you can see, there's a lot of gas being emitted from this lava lake. It's mostly water and carbon dioxide, but also contains sulfur, chlorine, and fluorine. In fact at sometimes up to two hundred tons a day of sulfur are emitted from this lava lake.
DOWN BELOW, ON THE SLOPES OF THE VOLCANO, NELIA'S COLLEAGUE BILL McINTOSH SHOWS WHAT HAPPENS WHEN FIRE MEETS ICE.
name title:
Bill McIntosh
Geologist, NM Inst. of Mining and Technology
Bill Macintosh:
We are inside an ice cave, on Mt. Erebus, and this is formed by heat, geo-thermal heat, rising from the lava, here, and melting the snow cover, producing this cavity. There are quite a number of caves on Erebus like this, several hundred.
THESE CAVES MAY HINT AT WHAT CONDITIONS MAY BE LIKE DEEP DOWN UNDER THE WEST ANTARCTIC ICE SHEET-AND EXPLAIN SOME OF THE ICE STREAMS STUDIED BY SRIDHAR ANANDAKRISHNAN.
McIntosh:
There is a pretty strong similarity between what's happening here in this ice cave, and what may be happening at the base of the Western Antarctic ice sheet. Where you have geo-thermal heat rising from active volcanoes causing melting at the base of the ice sheet, and in that case accumulating water which then may be lubricating the ice streams and causing them to flow more rapidly.
SO VOLCANOES LIKE EREBUS MAY HELP THE WEST ANTARCTIC ICE STREAMS SLIP OVER THE UNDERLYING ROCK AND SHAPE THE FUTURE OF THE PLANET.
OTHER RESEARCHERS READ ANTARCTICA'S ROCKS TO DISCOVER ITS PAST, TRACING THE LONG-TERM TEMPERATURE AND CLIMATE HISTORY OF THE CONTINENT, WHICH MAY ALSO GIVE US A PREVIEW OF WHAT'S TO COME.
titles: Reading the Rocks
THIS IS THE STORY OF "TWO DAVE'S", DAVID HARWOOD AND DAVE MARCHANT, BOTH OF WHOM ENJOY DOING RESEARCH OUT IN REMOTE ANTARCTIC FIELD CAMPS.
BOTH USE THE ROCK RECORD IN THEIR STUDIES... BUT WHAT THEY THINK THE ROCKS TELL US IS COMPLETELY DIFFERENT.
THEY AGREE THAT ANTARCTICA HAS BEEN MUCH WARMER IN THE PAST.
THEY DISAGREE ABOUT HOW RECENTLY-WHETHER THIS CONTINENT IS LOCKED IN A 10 MILLION YEAR DEEP FREEZE... OR WAS MUCH WARMER JUST 3 MILLION YEARS AGO.
David Harwood:
One view that we hold is that the ice sheet has been very dynamic, dynamic: growing ice sheets, shrinking ice sheets, growing ice sheets, shrinking ice sheets, through time.
Dave Marchant:
The volcanic ash story has told us that Antarctica has been a cold desert for 15 million years, and it's a frozen landscape.
LET'S SEE AND HEAR THEIR EVIDENCE AND HOW THEY TRY TO SOLVE THE QUESTION.
LIKE ALL GEOLOGISTS, DAVID HARWOOD USES THE LAYERS IN THE ROCKS TO TELL HIM WHAT ARE THE OLDEST, AND WHAT ARE THE YOUNGEST ROCKS.
SUPER:
David Harwood
Micropaleontologist, University of Nebraska, Lincoln
Dave Harwood:
If I were to try to tell you a history of this region, you can tell it because those rocks on the bottom had to be there before any other rocks could be laid on top of them. So they are older than the rocks on top.
WHEN HE LOOKS AT THE TRANSANTARCTIC MOUNTAINS HE SEES EVIDENCE THAT CONFIRMS THE DEEP HISTORY OF THE CONTINENT, SHAPED BY PLATE TECTONICS.
Dave Harwood:
What we see down here in the bottom of these kind of rough and rugged rocks, are igneous rocks that were intruded into this area at a time when all of the other continents, Africa, India, South America, Australia, were connected together.
On top of those, there's a dark band that you see, actually represents some glacial deposits, that are about 200 or 300 million years ago.
Above that we have some coal and some river deposits. The coal indicates the climate was wetter, but certainly much, much warmer than today.
HARWOOOD ALSO USES THE GLACIERS AS COLOSSAL EXCAVATION TOOLS, TAKING ADVANTAGE OF HOW THEY SCOUR OFF TOP LAYERS, REVEALING BURIED ROCKS AND SEDIMENTS.
Harwood
Sometimes I've turned myself, a garbage pile geologist, and that's in looking through these piles of glacial debris that the ice sheet has brought to these areas, we can then study them. It's a means of looking at what exists underneath the ice sheet.
DAVID HARWOOD AND HIS TEAM ARE OUT HERE, RAPPELLING DOWN STEEP CLIFFS, BECAUSE HE'S ON THE TRAIL OF ANCIENT LIFEFORMS THAT HAVE TURNED TO ROCK-FOSSILS THAT REVEAL WHAT THE TEMPERATURE AND CLIMATE OF ANTARCTICA MUST HAVE BEEN LIKE MILLIONS OF YEARS AGO.
title: ANTARCTIC DIATOMS (Sirius group... ) ON TAPE
Harwood:
The fossils I study are microscopic, I can only see them with a microscope. The organisms I study are called diatoms, they are one-celled plant plankton, they float out in the open seas, they live in lakes, they actually live on soils as well.
HIS BOTTOM LINE IS THAT SOME OF THESE FOSSILS PROVE ANTARCTICA WAS WARM ENOUGH FOR PLANTS JUST A FEW MILLION YEARS AGO.
Harwood:
We've actually found three million year old leaves, and pieces of wood, suggesting that these Antarctic slopes, as recently as three million years ago, were green.
DAVE MARCHANT READS THE ROCK RECORD VERY DIFFERENTLY.
SUPER:
David Marchant
Geomorphologist, Boston University
Dave Marchant:
In general, the pattern you see is a paralyzed landscape. All that's happened in the last thirty million years is a slight framing of the landscape.
MARCHANT'S EVIDENCE IS VOLCANIC ASH, DATED AT 10 MILLION YEARS AGO.
HE'S FOUND THE ASH COLLECTED IN A DISTINCTIVE PATTERN OF CRACKS, WHICH ONLY OCCUR WHEN TEMPERATURES ARE VERY LOW.
Marchant:
A huge volcanic eruption happened, in this case, 10.1 millions years ago, it's the date we have on this ash. It rained all over the Valleys, but was only trapped in these deep contraction cracks.
They've healed over, and we've stumbled upon one here in digging a pit, and as we went down through it, we saw pure volcanic ash, in sharp contact with the surrounding sediment.
This tells us that at 10.1 million years ago, Antarctica was a cold desert, much as it is today.
SO MARCHANT BELIEVES ANTARCTICA HAS STAYED DEEP-FROZEN FROM AT LEAST 10 MILLION YEARS BACK, RIGHT THROUGH 3 MILLION YEARS AGO-WHEN HARWOOD THINKS IT WAS WARMER-AND UP TO THE PRESENT DAY...
WHY IS THIS DEBATE ABOUT MILLION YEAR OLD ROCKS IMPORTANT?
Harwood:
By understanding how many times the ice sheet migrated and moved back and forth, it gives us some idea of how much potential there is for ice volume changes, ice sheet changes in the future.
STILL, THE JURY'S OUT...
FOR BOTH DAVE'S, AND FOR ALL TRUE SCIENTISTS, THE GATHERING OF SOLID EVIDENCE MUST PRECEDE AND THEN DICTATE THE VERDICT.
Harwood:
The only way we're going to resolve these two different views, one a "stablist" view, one a dynamic view, of the ice sheet, is by collecting more information. By working on these rocks that are here around us, by discussing the various bits of evidence, finding the weak points, posing the new questions.
HARWOOD AND MARCHANT MAY DISAGREE ABOUT WHAT THE ROCK RECORD SAYS, BUT THEY'RE UNITED IN THEIR LOVE OF THE CONTINENT AND THE RESEARCH PROCESS.
Marchant:
I'm speechless each time I come out here and find something like this. It's almost frightening to see how small we are. This is just one valley in Antarctica, and standing in the middle of it, you feel like a tiny ant. And that's just the immense proportions of Antarctica, but when you think of the time and history here, it's mind boggling, particularly when you can look at the surface, and it's 10 million years, or dig in an ash deposit, which landed one day 10.1 million years ago.
Harwood:
You figure that we're just six people out here working, and there's no one else for probably two hundred miles. You look across at the landscape, and it's virtually untouched. Secrets hidden around every corner, and you just have to keep your eyes open. That's the most rewarding... knowing that just about every corner, you could really advance the science somewhere.
THE ONLY THING THAT'S CONSTANT, SAID A GREEK PHILOSOPHER, IS CHANGE.
BUT SOMETIMES CHANGE IS HARD TO SPOT, AND THE EVIDENCE IS UNCERTAIN.
OUT HERE IN THE FIELD, SRIDHAR, HARWOOD AND MARCHANT ARE HELPING BY ASKING QUESTIONS AND PROVIDING ANSWERS.
OVER TIME, WE'LL KNOW THE TRUE STORY OF THIS AMAZING LAND OF FIRE AND ICE...
