Previous: Chapter Eighteen: The Isle of Youth
Bender had mail.
To: MaryLiz Bender
Cc: Clint Lex
From: P. J. McClintock
Subject: Inconveniently Deep Hole aka Pool of Xblanque.
Dear Dr Bender,
I received the completed lidar scans from Merl about 12 minutes
ago. Yep, the cenote you called Pool of Xblanque is indeed IDH,
Inconveniently Deep Hole. (Attached see Schindel and Currans,
1973, Fig. 2, p 4)
We have satellite imagery of the Hole back to the early 2000s
with ten meter resolution, and better than that for some years
since. As far as I know, you’re the first ever to scan the
entire surface at close range using LIDAR. There are more than
ten thousand cenotes in Yucatan, and only a fraction have been
mapped in detail.
The Pool of Xblanque, as you say that locals now call it,
occurs on survey maps back to the 1920s, just tagged by an
elevation contour: the interior has no detail indicated at all,
other than a green tint to indicate vegetation: the tree canopy
you saw yourselves. It appears that even at the time of the
first surveys, the sinkhole had a mature forest growing
on an island made of fallen slabs from the cave's original
ceiling. We colloquially call these features 'sinkholes',
but properly speaking, most cenotes in Yucatan are 'karst
windows', where an existing ancient underground passage
is penetrated from the surface via erosion or fresh
faulting. The passage minded its own business for millions
of years, then one day, the ceiling caves in. These
collapses, the cenotes, are way younger, geologically
speaking, than the cave passages that they penetrate. By
contrast, cave passages beneath sinkholes, properly termed,
were created by that surface interaction in the first
place. That's why the cenotes are 'karst windows', not
sinkholes.
Regarding the lack of detail in the early surveys, it's
a 60 meter rappel from the edge to the bottom. As a
consequence, it's little wonder that it was never
mapped by hand survey. Sic sunt draconis, as the old
cartographers used to say: "Here be dragons".
The name 'Inconveniently Deep Hole' crops up in cave
literature around the same time, in lists of cenotes in
Yucatan. The thing about the name “Inconveniently Deep Hole”
being a translation from Mayan is a myth, by the way, perhaps
an invention of yellow journalism later taken as fact. No one
knows what the feature was called by ancient people in the
area. Nowadays it's considered an insult to put names in the
mouths of ancient people.
Xblanque is not the largest cenote of the Yucatan, but large
enough so that it displays some classic features associated
with larger examples of such secondary karst structures. The
trees are indeed growing on islands of collapse, connected by
shallow pools above submerged breakdown resting on the cenote
floor. Agree with your friend (?) Jo Stapledon that the large
lighter colored mass in the center represents a flat plain on
the largest of these collapse structures, largely occluded by
tree canopy. A 3D rendered texture map of the reduced lidar
map plus video would be of inestimable value, but the
computing and staffing resources would be formidable, our own
"Hilltopper" quantum computer cluster would take years to
perform the analysis of your data set.
Am intrigued as to the greater scope of this research. I
searched the name of Jo Stapledon and the only reference I
could find was to a marsupial specialist in Australia.
Is there another Jo Stapledon?
Best,
P. J. McClintock
Center For Karst Topgraphy Analysis
Western Kentucky University
To: MaryLiz Bender, P. J. McClintock
Cc: Petra Lauer
From: Clint Lex, Ph.D.
Subject: Re: Inconveniently Deep Hole aka Pool of Xblanque.
Dear Dr Bender,
We received and unpacked your LIDAR data set this morning.
Dr Groves, our emeritus director, was in to give the
monthly coffee talk, but the star of the colloquium was
the holographic walk through of your model, the feature
you are calling the Pool of Xblanque.
Dr Groves is a pioneer in mapping and modeling caves,
going back to the 20th century, and it's difficult to get
anything over on that scientist. We hid the location of
the cenote in our presentation, as Dr Bender requested.
Still, at one point Dr Groves, sitting in the front row
in front of me, nodded, and mouthed the word 'Yucatan'.
I understand the sensitivity of your discovery, but
I nodded back.
To the question of ocean access to the cenote via air
filled cave passages, sea level rise during the period
1960-2050 may indeed have inundated (filled with water)
cave passages which were formerly filled with air, during
periods in history when the sea level was lower than
presently. But even given anthropogenic climate change,
that's not quite enough. Those cave passages have been
mostly filled with water since ages past.
Generally, the limestone of the Yucatàn is far younger
than comparable cave bearing rocks in Kentucky, only
65 million years old or younger. The ancient coral
reefs which form the cavernous limestones of the
Yucatan peninsula were lifted to the sky around ten
million years ago, after approximately 55 million years
of reef formation. The oldest documented passages in
Yucatàn are younger still, around 175,000 years old.
Sea levels have been stable in the region for
approximately 5,000 years. Although climate change
has led to slight increases in the last century,
the bulk of cave formation in Yucatan occurred
during a relative minimum in sea level as a result
of a global temperature minimum locking up water
ice at the poles.
Those old cave passages may or may not have been
large enough to allow human beings to pass through
them, even when filled with breathable air. But given
the size of the cenote, the potential remains for
discovery of large cave passages linking the cenote
to the Gulf of Mexico.
Attached please find an expanded XYZT file, with your
LIDAR data embedded in the USGS model for that segment
of the Yucatan Peninsula, the Woods Hole model for the
seafloor. The "T" in XYZT stands for "Time", by the way:
you can dial up any year you like, and the model will
show you the water surface for that year. My students
enjoy pulling up the timeframes representing storm
events (hurricanes), which shows a rare negative storm
surge. These momentary and local depressions in sea
level have two chief causes: a slight depression of sea
level occurs in regions of high atmospheric pressure.
The other, dominant mechanism is easier to understand.
As a violent tropical storm or hurricane blows past a
small bay, the local sea level may drop, with dramatic
effect, as the wind itself sucks water our of the
neighboring bay. These events have a time scale of scant
hours, but they are real. Such an event could, in theory,
introduce air to passages normally filled with seawater,
and postentially cycle breathable oxygen into air filled
pockets in some cave passages.
MaryLiz, your adventures in space are known to all of
us, here at the Center. I speak for all of us in
reminding you that water-filled caves are among the
most dangerous to explorers.
Before you enter a cave, please ensure that your team
understands the risks of underwater operations in the
cave environment. We are prepared to provide resources
in ensuring your team's safety, and hope to remain in
the loop on any further work in this area.
Sincerely yours,
Lex
Clynt Lex, Ph.D.
Center for Cave and Karst Studies
Western Kentucky University
Bender closed the lid of the laptop. There was the aroma of coffee. Gaby had set a cup next to Bender without the latter noticing. Bender took a slow sip.
Time to unplug and think. Bender slid open the screen door at the back of Gaby’s kitchen and took a seat on a platform rocker on the veranda. The sun was not quite up, but as the pre dawn glow gave way to sunrise, Bender could see the shadow of the house grow shallower, melting down the hillside on the other side of the tram railway, ultimatelt puddling, cosily, in the flower beds next to the family’s tram shed.
Bender turned her attention to last night’s visit from the Blue Helmets. UNESCO, the “blue helmets” charged with protecting the Earth’s natural resources, had been reasonable, but firm. Any wallabies living within the Pool of Xblanque were subject to absolute protection by force of international treaties meant to give voice to the voiceless species of planet Earth. The fact that the wallabies had been purposely bred during the Cold War meant that its location was so sensitive, it was absent from the UNESCO roster, effectively a planetary state secret.
Bender’s team’s innocence and naivete in visiting the protected cenote was the only way they all could possibly have made it there to collect the precious 3D map of the cenote, now carefully annotated by the WKU team to include the surrounding geology and hydrogeography.
They had jaunted to Yucatan without a thought to publicity. If they had announced the expedition, aforehand, all of this would have ended on the Progreso Quay.
Bender sighed.
On the plus side, since their intrusion was innocent UNESCO only demanded forgiveness, since it was far too late to ask permission. Aude et Effice.
It was late at night, and Bender was starting to lose focus. What was planned for tomorrow? There was something… what?
I remember. A day of rest for the whole team. I ordered it myself.
The Wallabies. How did they get inland to the Pool of Xblanque, so many miles inland from the Gulf?
From the sea… from the sea….
Bender’s phone beeped. Bender barely had the concentration to read the incoming message.
From: Captain Petra Lauer
To: MaryLiz Bender, P. J. McClintock, Clint Lex
Subj: Re: Inconveniently Deep Hole aka Pool of Xblanque.
Research vessel *Marcel Loubens* departing Port Arthur
with all speed. ETA 0700 Progreso time. Suggest Bender
& Co stay put in Yucatan pending arrival.
We think we can help.
Petra Lauer
I can do that. Bender slept.
Bender awoke at 6 AM to the aroma of fresh coffee.
Merl: “They’ll never let us back there.”
Cap spoke. “We may not need them to.”
Merl looked at Cap with a conspiratorial eye. “Stealth tech?”
“Ha. I neither confirm nor deny. Stealth isn’t the right word. But ‘tech’ might be.” MaryLiz glanced at Merl, and crossed to the coffee urn, which was empty. Bender opened a drawer and drew out a new packet of coffee.
“Not stealth, or stealth tech. But perhaps cover, of a sort. Academic cover.”
Merl snorted. “Your friends with fancy degrees are goin’ to save us from the most fanatical biological conservation group ever conceived?”
Our friends at WKU looked at our scans. The Pool is only a few thousand meters from the coast. There may be cave passages between the Pool and the sea. Unfortunately, they are all full of water.” Bender frowned on purpose. The Western Kentucky University people had been adamant on the risks to human safety.
Frances broke the silence. “Does UNESCO monitor the caves, too?”
“They’d like to,” replied MaryLiz. “But caves are tough – and expensive – to monitor in real time.
The coffee was ready. MaryLiz poured her second cup. Merl was staring at the screen, at the map of the Yucatan Peninsula.
“These blue dots,” said Merl, “they’re caves?”
“Cave entrances,” said MaryLiz. “They are all over the Yucatan. They all have water at the bottom. They’re natural formations, made when underground caves get so close to the surface that the ceiling collapses, all the way to the surface. There are thousands of them in Yucatan. They call them cenotes.”
Merl stepped back from the map. “Thousands.” Merl said. The map did show thousands of sinkholes.
Merl reached both hands out towards the map, palms down, thumbs touching, outlining a crude semicircle which covered most of the blue dots. “Why are the cenotes laid out like that? That curve is so smooth. Like I’d make with a drawing compass.”
No one knew. Bender loaded fresh grounds in the coffee urn.
Bender brought the discussion back to earth. “I don’t want to go behind UNESCO’s back on this. The last thing we need is be Federal trespassing charges in Mexico. I am just wondering how much we can learn, legally, without bothering them.”