A SA TAXI whisked me into Townsville in trop­i­cal north Queens­land, my eyes were drawn to the tallest ob­ject on the sky­line: a drilling der­rick, seem­ingly out of place in the har­bour.

Australian Geographic - - Wild Australia -

I soon recog­nised it as part of the JOIDES Res­o­lu­tion, a oneof-a-kind re­search ship equipped to drill deep into the ocean f loor and take core sam­ples. This was the very ship that was shortly to take 30 sci­en­tists, in­clud­ing me, on a nine-week sci­en­tif ic ex­pe­di­tion to probe the se­crets of the newly named eighth con­ti­nent of ‘Zealan­dia’.

This ex­tra­or­di­nary event is the f irst time a new con­ti­nent has been dis­cov­ered since Jan­uary 1820, when a Rus­sian ex­pe­di­tion, led by naval of­fi­cers Fabian Got­tlieb von Belling­shausen and Mikhail Lazarev, bat­tled treach­er­ous seas to reach an ice shelf along the coast­line of Antarc­tica. In do­ing so, they be­came the f irst peo­ple ever to set eyes on the frozen south­ern realm.

Less dra­matic, but per­haps more sur­pris­ing, was the an­nounce­ment by sci­en­tists in 2017 that Earth had an eighth mod­ern-day con­ti­nent. This one sank be­neath the waves 85–60 mil­lion years ago and was orig­i­nally big­ger than the In­dian sub­con­ti­nent of to­day. The only ves­tiges of this land mass that re­main above the ocean are New Zealand, New Cale­do­nia and the Aus­tralian ad­min­is­tered Nor­folk Is­land.

Un­known to ge­ol­o­gists, as much as 94 per cent of this con­ti­nent – Earth’s small­est in the mod­ern sense, with an area of con­ti­nen­tal crust cov­er­ing 4.9 mil­lion sq.km of the Pa­cific – had been hid­den right be­neath our noses.

While the name Zealan­dia was first used in 1995, it was the grad­ual ac­cu­mu­la­tion of data gath­ered dur­ing sev­eral decades, in­clud­ing satel­lite im­agery and grav­ity and depth maps of the ocean f loor, that ul­ti­mately led a group of sci­en­tists in New Zealand, New Cale­do­nia and Aus­tralia to pub­lish a pa­per in March 2017 in the jour­nal GSA To­day, off icially declar­ing it a new con­ti­nent.

It was this dis­cov­ery and the on­go­ing work to un­der­stand Zealan­dia that, sev­eral months later, saw me leave my home in the USA, where I am a pro­fes­sor of ge­ol­ogy at the City Univer­sity of New York, to join the ex­pe­di­tion depart­ing from Townsville dur­ing the Aus­tralian win­ter of 2017.

As part of the In­ter­na­tional Ocean Dis­cov­ery Pro­gram (IODP) ex­pe­di­tion aboard the JOIDES Res­o­lu­tion, our goal was am­bi­tious. We would drill ocean f loor cores from mul­ti­ple lo­ca­tions on or near Zealan­dia, re­cov­er­ing sed­i­ments from more than 850m below the sur­face that were laid down as much as 68 mil­lion years ago. We aimed to re­con­struct a pic­ture of the cli­mate and ge­ol­ogy of this lost con­ti­nent, go­ing all the way back to the age of the di­nosaurs.

SEE­ING THE 62m-high der­rick of the 143m-long JOIDES Res­o­lu­tion brought back mem­o­ries of my pre­vi­ous two ex­pe­di­tions on this mighty re­search ves­sel: on the f irst, we ex­plored the re­gion south of Tas­ma­nia, and on the sec­ond we tra­versed the icy waters off Antarc­tica. This time, I was to be an on-ship sed­i­men­tol­o­gist, one of a team of 30 sci­en­tists from a dozen dif­fer­ent coun­tries who had all been cho­sen to take part. To­gether, we made up IODP Ex­pe­di­tion 371, tasked with ex­plor­ing and un­der­stand­ing the his­tory of Zealan­dia.

The IODP is among the most suc­cess­ful of in­ter­na­tional sci­ence pro­grams. It has evolved over decades, gath­er­ing in­creas­ingly com­pre­hen­sive records on cli­matic and oceano­graphic changes dur­ing the past 100 mil­lion years by col­lect­ing hun­dreds of kilo­me­tres of sed­i­ment cores from ev­ery ocean f loor all around the world.

The work of the IODP is the pre-em­i­nent source of in­for­ma­tion for data older than 800,000 years, which is beyond what we can learn from ice cores ex­tracted from the planet’s great frozen ex­panses.

With 80 crew mem­bers and drillers on board, as well as the sci­en­tists, we left Townsville on 27 July 2017 for our f irst drill site, more than 2100km east of Aus­tralia. We planned to work at six dif­fer­ent drilling lo­ca­tions spread over a wide area, pen­e­trat­ing deep below the sea f loor af­ter ex­tend­ing pipes down through ocean depths of up to 4.5km.

My re­search would fo­cus on de­vel­op­ing cli­mate and oceano­graphic records from pre­his­toric times when lev­els of car­bon diox­ide (CO2) in the at­mos­phere were higher than they are to­day – in­for­ma­tion vi­tal for un­der­stand­ing the threat we face from cli­mate change to­day and into the fu­ture.

Lev­els of CO2 in our at­mos­phere have al­ready risen from 280ppm (parts per mil­lion) be­fore the in­dus­trial rev­o­lu­tion to more than 400ppm to­day – and are pre­dicted to rise to more than 500ppm be­fore the end of the cen­tury.

The work of palaeo­cli­ma­tol­o­gists has re­vealed that the last time the lev­els of CO2 in our at­mos­phere were as high as 500ppm was more than 25 mil­lion years ago. To achieve at­mo­spheric lev­els of CO2 equal to those that hu­man­ity has

man­aged in a mere two cen­turies, Mother Na­ture needed tens of mil­lions of years.

In a sense, look­ing at the cli­mate with this amount of green­house gas in the at­mos­phere al­lows us to use the past to look ‘back to the fu­ture’. These data are go­ing to prove in­creas­ingly valu­able as we head fur­ther into cli­matic con­di­tions far beyond any­thing pre­vi­ously ex­pe­ri­enced by our hu­man species.

ASIDE FROM CLI­MATE, we hoped to learn much more about the ge­olog y and geog­ra­phy of mys­te­ri­ous Zealan­dia. Only about 6 per cent of it re­mains above sea level – the largest pieces be­ing New Zealand and New Cale­do­nia. The rest of the con­ti­nent lies on av­er­age more than 1km be­neath the waves.

It has taken decades of painstak­ing un­der­wa­ter re­search us­ing seis­mic data (in­for­ma­tion from sound waves) to cap­ture images of the sed­i­ment and rock lay­ers below the sea f loor, as well as take core and dredge sam­ples, to de­ter­mine the true ex­tent of this vast sub­merged land­mass.

The com­bined pic­ture of this data has re­vealed Zealan­dia to have all the char­ac­ter­is­tics of a con­ti­nent, in­clud­ing the fact that its low-den­sity, sil­ica-rich rocks (char­ac­ter­is­tic of con­ti­nen­tal crust) are sig­nif icantly el­e­vated above the sur­round­ing sea f loor of the oceanic crust.

Zealan­dia has an amaz­ing his­tory. Like Aus­tralia, it was once part of the south­ern su­per­con­ti­nent Gond­wana – ac­count­ing for about 5 per cent of it – be­fore break­ing away from Aus­tralia and Antarc­tica about 80 mil­lion years ago. It then sank below the waves, qual­i­fy­ing it as a kind of a di­nosaur-era At­lantis. How­ever, the real mys­ter­ies oc­curred af­ter this. Data sug­gest it be­gan to rise once more, be­fore dis­ap­pear­ing un­der the waves for good (or at least un­til now). The tim­ing and ex­tent of its pre­vi­ous re-emer­gence is an area of hot de­bate.

Fur­ther­more, with­out knowing its pre­his­toric geog­ra­phy, sci­en­tists can only guess at what ef­fects Zealan­dia might have had on ocean cir­cu­la­tion and plan­e­tary cli­mate. In­deed, when we look back to this re­gion more than 25 mil­lion years ago, when CO2 lev­els were above 500ppm, there is a sig­nif icant dis­crep­ancy be­tween tem­per­a­tures es­ti­mated by cli­matic mod­els and those hinted at by data from rocks and sed­i­ments.

Un­der­stand­ing this con­fu­sion is im­por­tant be­cause these are the same kinds of cli­mate mod­els we’re us­ing now to pre­dict our cli­matic fu­ture in a rapidly warm­ing world. While much data has al­ready been col­lected on the ge­ol­ogy and geog­ra­phy of the long-sub­merged rocks of Zealan­dia, on this ex­pe­di­tion we were col­lect­ing deep-sea cores of sed­i­ment ca­pa­ble of giv­ing us a wealth of de­tailed in­for­ma­tion and un­lock­ing the his­tory of this mys­te­ri­ous con­ti­nent.

SIX DAYS IN, and we’d reached our f irst ex­plo­ration site. Drilling starts by low­er­ing a pipe through a hole in the ship’s hull called the moon pool. The pipe typ­i­cally ex­tends down through thou­sands of me­tres of wa­ter. Once it reaches the sea f loor, a spe­cial cor­ing bit drills in and re­cov­ers 9m of core sam­ple at time. The core sam­ple is pulled back up through the pipe to the ship where it’s car­ried by half-a-dozen sci­ence tech­ni­cians to a row of ta­bles. Here, they cut it into 1.5m lengths, de­ter­mine the age of each and then sub­ject the sec­tions to a bar­rage of tests – sen­sors de­tect nat­u­ral gamma rays, den­sity, mag­netic sus­cep­ti­bil­ity, ther­mal con­duc­tiv­ity and much more.

These records will ul­ti­mately pro­vide the data needed to un­der­stand the cli­mate and ge­o­log­i­cal his­tory of this land­mass many tens of mil­lions of years ago when parts of it were above the sur­face and pop­u­lated by pre­his­toric crea­tures.

At this f irst drill site, we were in for a big sur­prise. We drilled 300m below the sea f loor to study a baff ling fea­ture re­vealed by seis­mic data that had led to wild spec­u­la­tion. Ex­cite­ment built as we drilled closer to the fea­ture, f irst reach­ing a sed­i­ment layer that turned out to be 40 mil­lion years old and had been de­posited in shal­low wa­ter.

Im­me­di­ately below we found vol­canic rocks that formed when Zealan­dia had risen up. The vol­canic lay­ers were geo­chem­i­cally al­tered by an­cient sea wa­ter, re­sult­ing in the most beau­ti­ful coloured rocks. These were dated to a time when, else­where on the planet, early pri­mates were swing­ing through trees and great horn­less rhino-like crea­tures had reached the size of di­nosaurs.

We were all thrilled, be­cause now we had ages and wa­ter­depth es­ti­mates for when some of these rock lay­ers were de­posited, which we could ap­ply to lay­ers else­where, help­ing us to start build­ing a ge­o­log­i­cal map of this part of Zealan­dia. This was sup­posed to be among the least in­ter­est­ing of the drill sites and yet here we were cel­e­brat­ing ex­cit­ing new dis­cov­er­ies.

Af­ter this f irst sur­prise, it was on to our next three drill sites, each lo­cated on the slopes of deep-wa­ter basins in Zealan­dia. The sec­ond two were fur­ther east, one di­rectly south of New Cale­do­nia and the other di­rectly north of New Zealand, with the fourth site lo­cated be­tween New Zealand and Aus­tralia.

The his­tory of each of these re­gions of Zealan­dia had been shrouded in mystery around when they first sub­sided and if

Look­ing at the cli­mate with this amount of green­house gas in the at­mos­phere al­lows us to use the past to look ‘back to the fu­ture’.

they had ever risen above sea level again. At the two east­ern sites we re­cov­ered sed­i­ments up to 50 mil­lion years old, from a time when Earth was much warmer than to­day, due in part to high CO2 lev­els. At the site be­tween Aus­tralia and New Zealand, we re­cov­ered sed­i­ments dated to 67 mil­lion years ago, when di­nosaurs still roamed the planet and very shortly be­fore their demise in a mass ex­tinc­tion.

The sed­i­ments ex­tracted from all three sites bore ev­i­dence of the tremen­dous power of na­ture. Grav­ity had gen­er­ated an­cient un­der­wa­ter avalanches that scoured the sea bot­tom as they rum­bled down from shal­lower waters into the abyss of these deep tec­tonic de­pres­sions.

Most of the sed­i­ments were com­posed of mi­cro­scopic shells formed by sin­gle-celled plank­tonic crea­tures known as foraminifera. These have been around since crea­tures first be­gan build­ing shells more than 500 mil­lion years ago. They live within sea-f loor sed­i­ments as well as f loat­ing in the up­per few hun­dred me­tres of the ocean and cre­ate fan­tas­ti­cally in­tri­cate shells. It seems in­cred­i­ble that sin­gle-celled crea­tures each less than half a mil­lime­tre across can form such beau­ti­ful and var­ied de­signs. Some are in the shape of a whorl, like a snail, while oth­ers are more ab­stract geo­met­ric styles.

Foraminifera are also in­cred­i­bly use­ful for sci­en­tists who study past cli­matic and oceanic changes, be­cause they re­veal clues to pre­his­toric wa­ter tem­per­a­ture, acid­ity, CO2 lev­els, ocean pro­duc­tiv­ity, and vol­ume of ice at the poles.

MANY WEEKS INTO our nine-week jour­ney, at the sec­ond and fourth drilling sites, we saw twisted lay­ers on the ocean f loor that were ev­i­dence of mas­sive blocks of sed­i­ments that had slid down the tilted slopes deeper into the abyss.

The re­peated fold­ing of in­di­vid­ual sed­i­men­tary lay­ers re­sulted in a great chaos of rock – an an­ar­chy of strata, where sed­i­men­tary beds re­peated. To add fur­ther con­fu­sion to this ca­coph­ony of sed­i­ments, we also found ev­i­dence of vol­ca­noes, be­cause these un­der­sea avalanches con­tained rock that orig­i­nated deep within the Earth. In the re­mote past, some­where on Zealan­dia, vol­canic moun­tains belched f ire.

While the ac­tual vol­ca­noes no longer ex­ist – and there­fore their ex­act lo­ca­tion is hid­den – we found vol­canic de­bris in many of our sed­i­ment cores span­ning a pe­riod of 20 mil­lion years at the sec­ond and third drilling sites.

With these cores, we were able to de­ter­mine ages and wa­ter depths for the f irst time in each of the basins we drilled, as well as re­veal­ing the size and scope of the an­cient avalanches, earthquakes and vol­canic erup­tions. For the f irst time, we were re­con­struct­ing the pre­his­toric ge­ol­ogy and geog­ra­phy of this mys­te­ri­ous con­ti­nent.

Our sixth and f inal site was off the con­ti­nent it­self, in deeper waters that plunge down to more than 4.8km, be­tween Aus­tralia and Zealan­dia.

Though our time was lim­ited, we col­lected cores from great depths that are help­ing us un­der­stand why there ap­peared to be fold­ing of the rock lay­ers, de­spite the fact it was seem­ingly far from tec­tonic ac­tiv­ity. Ge­o­log­i­cal quirks had re­sulted in the sed­i­ments be­ing bright colours, and they some­times con­tained ex­otic pink min­er­als that de­lighted our eyes af­ter eight weeks out at sea. But by then our ad­ven­ture was al­most over.

FI­NALLY, THE JOIDES RES­O­LU­TION sailed into Ho­bart on 26 Septem­ber. An amaz­ing ex­pe­di­tion had ended, with the sci­ence team hav­ing bonded in a way that only hap­pens when you are mu­tu­ally gripped by the magic of ex­plo­ration and dis­cov­ery. Our f irst evening in port was f illed with cel­e­bra­tory drink­ing and eat­ing as well as a few tears over our im­pend­ing de­par­ture.

We have since re­turned to our re­spec­tive na­tions and aca­demic in­sti­tu­tions to work on the thou­sands of sam­ples col­lected. I have stu­dents study­ing sam­ples from 17–15 mil­lion years ago, when CO2 lev­els in the at­mos­phere were higher than to­day, as well as 15–7 mil­lion years ago, when lev­els were more like those in re­cent pre-in­dus­trial times. How­ever, the bulk of our work will fo­cus on map­ping out the ge­ol­ogy and geog­ra­phy of Zealan­dia over time. Pre­lim­i­nary re­sults seem to conf irm a hy­poth­e­sis that the con­ti­nent rose up dra­mat­i­cally be­tween 55 and 34 mil­lion years ago.

But we have also come to re­alise that the pre­his­toric geog­ra­phy of Zealan­dia can’t be in­ferred sim­ply by look­ing at its shape to­day. The next step is to in­te­grate all the dif­fer­ent kinds of data to model how the con­ti­nent has changed over the past 65 mil­lion years.

As a re­sult of the ex­pe­di­tion, we even­tu­ally plan to cre­ate high-res­o­lu­tion oceano­graphic and cli­matic records for those 65 mil­lion years. The goal for us is to re­write the tec­tonic, geo­graphic, cli­matic and oceanic his­tory of this new con­ti­nent.

While the ex­pe­di­tion of a life­time may be over, the real sci­en­tif ic ad­ven­ture is about to be­gin as the re­searchers and aca­demics of Ex­pe­di­tion 371 be­gin de­ci­pher­ing the many se­crets of the lost con­ti­nent of Zealan­dia.

For the first time, we were re­con­struct­ing the pre­his­toric ge­ol­ogy and geog­ra­phy of this mys­te­ri­ous con­ti­nent.

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