Speaker 1: Welcome to Brainstuff, a production of iHeartRadio. Hey brain Stuff
Speaker 1: Lauren Bogelbaum here. In the decades after World War Two,
Speaker 1: the United States and the USSR locked into the space
Speaker 1: race to orbit and the Moon, but they were also
Speaker 1: vying to outdo each other in another race, one to
Speaker 1: the center of the Earth, or at least as close
Speaker 1: to it as possible. This resulted in the deepest hole
Speaker 1: in the world today, let's talk about the Cola Super
Speaker 1: Deep Borehole. Okay. In nineteen fifty eight, America launched Project Mohole,
Speaker 1: a plan to retrieve a sample from Earth's mantle by
Speaker 1: drilling to the bottom of the Pacific Ocean off of
Speaker 1: Guadalupe Island, Mexico. With funds from the National Science Foundation,
Speaker 1: they drilled six hundred and one feet that's one hundred
Speaker 1: and eighty three meters into the seabed before funding for
Speaker 1: the project was pulled in nineteen six sixty six. In
Speaker 1: nineteen seventy, the Soviets launched their attempt, drilling into the
Speaker 1: ground on the Cola Peninsula in the northwestern corner of Russia,
Speaker 1: just off the Norwegian border, near the Barren Sea. They
Speaker 1: were more successful, penetrating much deeper and collecting samples that
Speaker 1: still whole scientists. If you've visited the site today and
Speaker 1: you can it's a tourist attraction. Now, it might seem underwhelming,
Speaker 1: hidden in an abandoned work site, among rotting wood and
Speaker 1: sheets of scrap metal remains of the housing and drilling
Speaker 1: framework that once stood. There sits a small, unassuming, heavy
Speaker 1: duty metal cover secured into place with a dozen large
Speaker 1: resting bolts. Underneath this bottle cap is a hole that's
Speaker 1: just nine inches that's twenty three centimeters in diameter, but
Speaker 1: remains the world's deepest man made hole. It's actually the
Speaker 1: deepest point that we know of in the Earth. The
Speaker 1: Cola Super Deep Borehole runs about seven point six miles
Speaker 1: that's twelve point three kilometers into Earth's surface. For perspective,
Speaker 1: the hole's depth is the height of Mount Everest and
Speaker 1: Mount Fuji stacked on top of one another. It's deeper
Speaker 1: than the deepest point of the Ocean, the Marianna Trench,
Speaker 1: which dips a mirror six point eight miles or ten
Speaker 1: point nine kilometers below the surface of the Pacific. Drilling
Speaker 1: at Cola began on May twenty fourth of nineteen seventy
Speaker 1: The goal was to go as far as possible, which
Speaker 1: scientists at the time hoped to be about nine miles
Speaker 1: or fifteen kilometers. By nineteen seventy nine, the project had
Speaker 1: broken all world records for man made holes when it
Speaker 1: surpassed about six miles or nine and a half kilometers.
Speaker 1: In nineteen eighty nine, they reached the current depth. That's
Speaker 1: when temperatures in the well increased to three hundred and
Speaker 1: fifty six degrees fahrenheit or one eighty celsius, forcing work
Speaker 1: to stop. Turns out that digging a hole to the
Speaker 1: center of the Earth is a bit trickier than the
Speaker 1: researchers expected. When drilling began at Cola, the granite near
Speaker 1: the surface was easy going, but when drillers reached about
Speaker 1: four point three miles or six point nine kilometers deep,
Speaker 1: the layers became more dense and difficult to bore into.
Speaker 1: Drill bits broke, and the team had to change the
Speaker 1: direction of the drilling several times, meaning that there are
Speaker 1: a few branches off of the central hole. The resulting
Speaker 1: pattern looks a little like a Charlie Brown Christmas tree.
Speaker 1: The engineers plowed on, but the deeper they went the
Speaker 1: hotter the earth became. The temperature gradient conformed to what
Speaker 1: scientists had predicted to a certain point, but then the
Speaker 1: heat intensified. They weren't expecting anything higher than the boiling
Speaker 1: point of water, which is two twelve fahrenheit or one
Speaker 1: hundred celsius. When the temperature climbed eighty percent higher than that,
Speaker 1: the rock, which was also more porous that expected, started
Speaker 1: behaving more like a plastic that a solid, rendering drilling
Speaker 1: virtually impossible. Although the team pressed on until nineteen ninety two,
Speaker 1: they never got any deeper than what they reached. In
Speaker 1: nineteen eighty nine. The drill site was officially shut down
Speaker 1: and the hole sealed over in two thousand and five.
Speaker 1: But okay, why would anyone go to the trouble of
Speaker 1: doing this? Of course, humans dig holes for various reasons,
Speaker 1: most notably for extracting resources like fossil fuels and metals.
Speaker 1: For example, in the United States, there's the Bingham Canyon
Speaker 1: copper mine in the mountains near Salt Lake City, the
Speaker 1: site of a pit that extends three quarters of a
Speaker 1: mile deep that's one point two kilometers, and Oklahoma's Bertha
Speaker 1: Rogers gas well, which goes down about six miles or
Speaker 1: nine point six kilometers and had to stop because they
Speaker 1: hit liquid sulfur. The colibor hole was partially looking for
Speaker 1: the presence of metals and minerals down in the layers
Speaker 1: of Earth to help locate their deposits, but holes are
Speaker 1: also dug in the name of science to learn more
Speaker 1: about hazards like earthquakes and volcanic eruptions, resources like geothermal
Speaker 1: heat and energy, the evolution of our planet and the
Speaker 1: life on it, and the environmental changes of the past
Speaker 1: to better project into the future. For the article of
Speaker 1: this episode is based on how Stuff Works. Spoke with
Speaker 1: doctor Ulrich Hahnes, now the Liaison officer for the International
Speaker 1: Continental Scientific Drilling Program at the GFC Hemholtz Center for
Speaker 1: Geosciences in Germany. He's visited the Colobar Hoole, browsed the
Speaker 1: repository of core samples, and even laid hands on the
Speaker 1: now defunct well head. He explained one example in detail
Speaker 1: is that observations very close to an earthquake zone allow
Speaker 1: researchers to monitor the initiation and propagation of even the
Speaker 1: tiniest earthquake. In response to stress and strain We want
Speaker 1: to recover these near field physical, chemical, and mechanical data
Speaker 1: to fundamentally understand these processes that cannot be simplified in
Speaker 1: lab experiments or computer models. In nineteen seventy, when work
Speaker 1: on the Colo Peninsula began, the idea that the Earth
Speaker 1: has layers made up of different materials in different conditions
Speaker 1: was relatively new. Until the late eighteen hundreds, scientists believed
Speaker 1: that Earth's composition was the same from crust to core.
Speaker 1: But as the technology advanced to measure earthquakes, you know,
Speaker 1: seismic waves moving through the Earth, researchers discovered something bewildering.
Speaker 1: There was a sudden increase in the velocity of seismic
Speaker 1: waves as they passed from what we now know is
Speaker 1: the thin solid crust at the Earth that we stand on,
Speaker 1: to the underlying liquid mantle. If Earth's interior was made
Speaker 1: up of the same material all the way through, the
Speaker 1: waves should have been proportional to their distance. In other words,
Speaker 1: they should have moved gradually slower as they got further
Speaker 1: away from the quake's epicenter. But instead they started traveling faster.
Speaker 1: The seismic waves are refracted faster through denser materials, so
Speaker 1: researchers realized that those faster moving waves must have encountered
Speaker 1: a denser layer of Earth. This was first observed by
Speaker 1: a Croatian meteorologist and seismologist by the name of Andrea
Speaker 1: Mohorovicic in nineteen oh nine, who went on to publish
Speaker 1: his hypothesis about there being a discernible dividing line between
Speaker 1: Earth's crust and mantle a decade later. This boundary zone
Speaker 1: is known today as the Mohorovicic discontinuity or the MOHO
Speaker 1: It's what the American drilling team named Project Mohole after.
Speaker 1: Throughout the nineteen fifties and sixties, another earth shattering hypothesis
Speaker 1: was emerging. The idea of plate tectonics. The more general
Speaker 1: theory that the continents are aren't fixed, but rather shift
Speaker 1: over eons of time, went back to nineteen twelve, but
Speaker 1: it wasn't until nineteen fifty six, during a survey of
Speaker 1: the Pacific Ocean floor, that scientists observed real evidence of
Speaker 1: this in the form of on opposite sides of a
Speaker 1: ridge on the seafloor symmetrical magnetic reversals, meaning that both
Speaker 1: sides had been formed at the same time from the
Speaker 1: ridge line and then spread apart from each other. So
Speaker 1: when Project Mohole and the Cola Borehole began work, digging
Speaker 1: deep was an exciting field of study and a flex
Speaker 1: of a country's capacity with tech and engineering, similar to
Speaker 1: the space race. We knew even then that the Earth's
Speaker 1: crust must be relatively thin. On average, we think it's
Speaker 1: about twenty five miles thick. That's forty kilometers, though it
Speaker 1: tends to be thinner under the ocean floor and perhaps
Speaker 1: obviously is thicker when you come across a mountain range.
Speaker 1: The Cola team was hoping to dig down a little
Speaker 1: over a third of that, but got stuck a little
Speaker 1: under a third. The next layer down the mantle is
Speaker 1: probably the thickest layer. It should continue for another one thousand,
Speaker 1: eight hundred miles or three thousand kilometers, and seems to
Speaker 1: consist of hot, dense rock that flows like asphalt and
Speaker 1: moves the plates of the crust around. Underneath that, we
Speaker 1: think that there is the liquid metal outer core, which
Speaker 1: descends another one thousand, four hundred miles or two thousand,
Speaker 1: two hundred kilometers or so, and then the solid metal
Speaker 1: inner core, a hot dense ball of mostly iron with
Speaker 1: a radius of about eight hundred miles or one thousand,
Speaker 1: two hundred kilometers. So while the super Deep Borehole is impressive,
Speaker 1: it only penetrates less than a third of Earth's crust
Speaker 1: and just zero point two percent of the entire distance
Speaker 1: to the center of the Earth. And until we actually
Speaker 1: physically interact with these layers, we won't know for sure
Speaker 1: what they're made up above in what conditions those materials
Speaker 1: are under. Other attempts have been made through the years
Speaker 1: by other countries, including Germany, Austria, and Sweden, and a
Speaker 1: couple of oil wells have gone deep too, including one
Speaker 1: in the Persian Gulf and one off the southeast coast
Speaker 1: of Russia. None of those are deeper than the Kolo
Speaker 1: super Deep Borehole, though some are longer having veered off
Speaker 1: of their vertical courses. So we still haven't come anywhere
Speaker 1: close to reaching the Moharrevichic discontinuity and finding out whether
Speaker 1: we're right about the deeper layers of the Earth. Still,
Speaker 1: scientists discovered a lot from the Kola Boorhole and the
Speaker 1: other projects, as well a lot of today's drilling technology
Speaker 1: in use by both scientific teams and petroleum Companies, was
Speaker 1: first developed on the fly for Project Mohol or the
Speaker 1: German Continental Deep Drilling program. The Kola borhole taught us
Speaker 1: that a few of our hypotheses about the crust were wrong,
Speaker 1: like how quickly the temperature rises, and also that there's
Speaker 1: no conrad discontinuity, a transition boundary from granite rock to
Speaker 1: basalt that geologists had reasoned to exist based on results
Speaker 1: of seismic reflection surveys. The team also found liquid water
Speaker 1: far deeper than we previously thought could exist, Harms said.
Speaker 1: One of the unexpected results was certainly the occurrence of open,
Speaker 1: saline water filled cracks, documenting that the crust is not dense,
Speaker 1: but that pathways exist, allowing fluids to flow. Even more
Speaker 1: exciting was the discovery of biological activity among the rocks.
Speaker 1: At about four and a half miles down that's seven kilometers,
Speaker 1: the team found dozens of fossils from single celled marine
Speaker 1: organisms dating back two billion years. Some microscopic fossils, encased
Speaker 1: and organic compounds were surprisingly intact despite the extreme pressures
Speaker 1: and temperatures of the surrounding rock. But can we dig deeper?
Speaker 1: Probably eventually, but Harms said. Digging deeper than twelve kilometers
Speaker 1: depends on two critical factors temperature and borehole stability, the
Speaker 1: latter being dependent on stress strain and drilling fluid composition
Speaker 1: and weight. That'll take some pretty technologically advanced equipment. Considering
Speaker 1: that temperatures there are predicted to be as high as
Speaker 1: five hundred degrees fahrenheit or two fifty celsius, and the
Speaker 1: real pie in the sky, or rather pie in the
Speaker 1: Earth would be reaching Earth's mantle, Harms said, we can
Speaker 1: learn a lot about the mantle if we get access
Speaker 1: through drilling. Earth scientists want access to the real institu
Speaker 1: mantle to understand the nature of this boundary that is
Speaker 1: still debated and from which we have no fresh samples
Speaker 1: that contain information on how the crust and mantle interact,
Speaker 1: how fluids and magma droplets escape from the mantle into
Speaker 1: the crust and ultimately into our hydrosphere, and how they
Speaker 1: feed the biosphere, or how matter escapes back into the mantle.
Speaker 1: These grand circles of how our planet evolves remain enigmatic
Speaker 1: along this boundary, and moho discontinuity is therefore a prime
Speaker 1: objective of scientific exploration. But people are trying for it.
Speaker 1: In the early two thousands, Japan began work on a
Speaker 1: gigantic drilling ship called the chiqu A Japanese word for
Speaker 1: the Earth, which is designed to pick up where Project
Speaker 1: Mohol left off, going for the mantle through the relatively
Speaker 1: thin oceanic crust. This ship and others like it, have
Speaker 1: been part of several international science programs over the past
Speaker 1: couple of decades, co funded by multiple governments. In twenty
Speaker 1: twenty one, a Japanese team working with one of these,
Speaker 1: the International Ocean Discovery Program, achieved the deepest yet drill
Speaker 1: into the ocean's crust, coming in at four point nine
Speaker 1: miles or write over eight kilometers. Funding from the United
Speaker 1: States has since shifted away from scientific ventures like this again,
Speaker 1: but the international community is boring on. We'll keep you
Speaker 1: updated in the future. Today's episode is based on the
Speaker 1: article why did the Russians seal up the deepest holl
Speaker 1: in the world on how Stuffworks dot Com, written by
Speaker 1: Jennifer Walker. Journey brain Stuff is production of iHeartRadio in
Speaker 1: partnership with how Stuffworks dot Com and is produced by
Speaker 1: Tyler Quain. For more podcasts my heart Radio, visit the
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Speaker 1: favorite shows.