In early May, Kilauea, a volcano
on the southeast corner of Hawaii’s Big Island, began erupting,
and a suite of earthquakes, the largest with a 6.9 magnitude, shook
the island. The quakes caused fissures and cracks to open in the ground,
and lava has been pouring down the flanks of the volcano ever since.
The exact path the lava has taken has been as unpredictable as
it has been destructive. As of early July, the encroaching lava had
destroyed 700 homes and had flowed over at least 26 km2
, reaching the sea. Monitoring the damage
from the red-hot rock is hazardous, to say the least. But that is
what a number of scientists from the U.S. Geological Survey are doing,
both on the summit and on the lower East Rift Zone, with help from
drones.
Although this on-site data collection is invaluable
to scientists
seeking new information about how lava works, it’s not the
only way researchers amass knowledge about which way it will flow.
Armed with furnaces and some heavy-duty safety equipment, geoscientists
are making their own lava in the lab and measuring its behavior. These
researchers are making important contributions to efforts to understand
and better manage future lava flows.
Hot rocks
In Syracuse,
N.Y., a place not normally associated with volcanic
activity, Jeffrey A. Karson runs a laboratory capable of generating
hundreds of kilos of molten lava and flowing it across a few meters
of earth.
A research team at Syracuse University creates and pours
pahoehoe-like
lava from its kiln. Credit: Syracuse Lava Project.
Experimenting with lava in a lab isn’t as off
the wall as
it sounds, says Karson, who cofounded Syracuse University’s
Department of Earth Sciences. “Lava’s just molten rock.
If you have a furnace that’s hot enough, you can melt rock.”
Karson and his team use a crucible, akin to a giant Crock-Pot, heated
by a surrounding furnace to 1200 °C to generate lava.
The
researchers don’t work with just any old rock. They
collect billion-year-old basalt—ancient lava—from Wisconsin,
on the Midcontinent Rift System. “We use lava that has the
same composition as real, natural basaltic lava, which is a mix of
crystals and glass,” Karson says. “Around half of basalt
is silica, resulting in a mixture of glass and minerals, including
iron-rich pyroxene and magnetite. This is similar to the composition
that is erupting in Hawaii now,” he adds. It’s also
typical of the lava erupted in Iceland and other major rift zones
where most of Earth’s volcanic activity occurs, he explains.
Karson and his team are creating and pouring lava under various
conditions to answer a range of questions about volcanic activity,
both on Earth and other planets. Their work is directly relevant to
the ongoing eruption in Hawaii, where lava has been creeping over
the landscape, sometimes at speeds up to 35 km/h, swallowing homes
and coastline.
In particular, the Syracuse team has investigated
how a shell,
or crust, forms on lava as it cools and how that shell of hardened
lava determines the path of a flow and the shape it takes. Understanding
crust formation might help with mitigating or diverting certain kinds
of flows. For instance, firefighters on the Icelandic island Heimaey
successfully sprayed water on lava to accelerate crust formation when
the volcano Eldfell erupted in 1973. The approach saved the island’s
harbor from destruction.
Of all the different types of basaltic
flows, so-called pahoehoe
lava flows are the ones Karson’s team mainly mimics in the
lab. These Hawaiian-named formations are smooth and have tapestry-like
folds that develop as molten rock oozes across a surface. Think of
syrup as it’s squeezed from a bottle onto a stack of pancakes.
Rather than focusing just on crust formation, Karson has lately
worked to scrutinize lava as it flows over different surfaces to learn
about its behavior.
“Lava from Kilauea is flowing over
older lava, vegetated
ground, and of course houses and roads,” and each different
surface would make the lava flow in a distinctive way, Karson says.
He and his team have observed that lava can slip very quickly downslope
on wet surfaces. “This has not been observed in nature, but
then not many lava flows have actually been witnessed under the appropriate
conditions,” Karson says. The researchers hope that these behaviors
they’re observing in the lab will one day be used to model
real-world scenarios and help disaster management officials make better
decisions to keep people and property safe.
This image,
taken by helicopter on May 19, shows lava flowing over
Kilauea’s lower East Rift Zone. Credit: U.S. Geological Survey.
The Syracuse
research program is the largest of its kind in terms of
the scale at which the homemade lava is created and poured, but it’s
by no means the only one to take on lava in the lab.
Einat Lev,
a geoscientist at Columbia University, explores lava flows in her
own lab by using lava proxies—wax, clay slurries, and sugar
syrups—that have a viscosity similar to pahoehoe flows. She
also collaborates with the researchers at Syracuse, borrowing their
lava-pouring equipment to study molten basalt flows, pouring lava
on scales ranging from 10 cm to 2 m and comparing results to her proxies.
In 2015, Lev and her colleagues used both syrup and molten basalt to investigate what
happens to the path of flowing lava when obstacles
get in its way. They first ran the sugary syrup down slopes and into
simple flat or V-shaped obstacles and measured how the syrup diverted
around either side of an obstacle to create what’s known as
a bow wave. In some cases the syrup would eventually collapse over
the obstacle, allowing the flow to continue. Follow-up experiments
with molten basalt replicated the researchers’ findings.
Einat Lev’s group at Columbia University tested how both
syrup and homemade lava (shown) flow around obstacles in a formation
known as a bow wave. Credit: Nat. Geosci.
By tinkering with the shape, size, and orientation of
the obstacles
put in the syrup’s (and lava’s) path, the Columbia team
found ways to control the flow. A long, tall barrier at roughly a
right angle to the encroaching lava could slow the flow. A series
of shorter barriers stacked behind one another down the slope over
which the lava would flow also worked.
Lev says knowledge about
how these barriers affect lava is directly
applicable to the current eruption on Hawaii because it “helps
to predict how much a lava flow will inflate behind a berm or a house
and how fast it will move once it passes the obstacle.”
Thimblefull
of lava
But making tons, or even grams, of lava isn’t
practical
for every lab. Geoscientist Olivier Namur at KU Leuven and his colleagues
heat their samples inside small gold or platinum crucibles just millimeters
long and weighing around 50 mg. For Namur’s purposes, those
tiny amounts of molten rock are enough to understand what’s
happening on a larger scale, he says. On a practical level, smaller
is also better because the team’s furnace can maintain stable
temperatures only on this scale, gold and platinum crucibles are costly,
and a small sample can reach chemical equilibrium in the furnace more
quickly, cutting down experiment times.
Namur is interested
in what happens pre-eruption, deep underground
in volcanoes, so technically, the material he and his team are working
with could be considered magma rather than lava. He says that understanding
how magma behaves in the underground pipework of volcanoes could help
scientists better predict how the molten rock makes it to the surface
in an eruption and how it behaves afterward.
Olivier
Namur’s team at KU Leuven uses these small gold
crucibles (20 mm by about 3 mm) to hold and melt tiny amounts of synthetic
magma. Credit: Lennart Fischer.
To create
its synthetic magma, Namur’s team uses a mixture
of high-purity silicate, oxide, and carbonate powders, including Fe2O3 and K2CO3.
The researchers
stir the powders together in ethanol or acetone to make small quantities
of faux magma. For larger and more homogeneous quantities, they melt
the powders in a furnace at 1,600 °C over a number of cycles.
Namur’s latest study revealed some surprises about the composition of
magma and could even aid mining efforts.
By recreating
in their furnace the temperature and pressure of
a volcanic magma chamber—1000–1040 °C and about
1000 times the atmospheric pressure of that on Earth—Namur
and his colleagues found that their molten material split into two
immiscible liquids: one rich in silica and one rich in iron. This
observed split solves a conundrum about how certain volcanic landscapes
are mysteriously rich in iron ore, the team contends.
Namur
speculates that the finding could help mining operations
find new iron-ore deposits: Working out what eruption conditions are
needed to create this type of immiscibility could help prospectors
predict where to find iron-rich ores. So far, Namur says, his team
has learned that “to reach immiscibility, we need water in
the magma and oxidizing conditions.”
All this work raises
the question of how well synthetic lava and
magma replicate the real deal, coming from actual volcanoes at scales
many orders of magnitude larger than even those used by the Syracuse
program. While sugary syrup seems miles away from a volcanic outpouring,
the results are translatable, Columbia’s Lev argues. For instance,
“Syrup is actually close in its viscosity to the runny lavas
of Hawaii when they are still very hot,” she says.
For
the wider volcanology community, these lab simulations provide
crucial data and save geoscientists the prospect of dangerous fieldwork.
“Volcanic processes happen fast and at high temperature, and
in the wild can be both difficult and dangerous to access,”
says David
Pyle, a volcanologist from the University of Oxford. “Laboratory
simulations of lava flows have the advantages that they can be carefully
controlled, observed, and measured, and even if they are run on a
physically much smaller scale than the real-world examples, offer
scientists a safe and reproducible way of testing their simplified
physical and computational models of flowing lava,” he says.
Karson says he works hard to make Syracuse’s experiments
relevant for the real world. “Our large-scale experiments create
lava flow lobes that are within the range of those that form in natural
pahoehoe flows,” he says. “Natural flows are not just
giant continuous sheets,” he adds. Rather, they are a pile
of small lobes, similar to the ones he makes.
But he also contends
that experiments on all different scales are
necessary to form a more complete picture. “Our experiments
bridge the gap between field studies of natural lava flows, which
are dangerous and impossible to make measurements on, and other types
of experiments,” he says. These other experiments include studying
the physical properties of much smaller amounts of lava and analog
experiments like those Lev has done, as well as numerical models.
Like all models—whether analytical, computational, or experimental—lab
lava studies are best thought of as offering a “toy view”
of the natural world, Pyle says. “But well-designed experiments
give us a chance to observe, close up, things that we would never
be able to see in nature,” he adds. “Best of all, the
by-products of the lava pours are wonderfully glossy pieces of volcanic
glass. And who wouldn’t want one of those on their mantelpiece?”
As the eruption
at Kilauea continues, and the lava flow pushes ever onward,
it’s likely that lab-made lava and magma might one day inform
emergency personnel’s efforts to limit lava damage and perhaps
even save lives and properties from destruction.
Katharine Sanderson
is a freelance contributor to
Chemical & Engineering
News
, the weekly newsmagazine of the American
Chemical Society. A version of this story appeared in C&EN.