- Dr. Alison Graettinger
Thanks to an invitation to talk about rocks, something I am sure you can tell I enjoy, I got the opportunity to travel to Marrakech, Morocco in June. Talking about my research is an important and enjoyable part of my job. It is a means of sharing the latest results, reaching out to groups who study different but related fields, letting the public know what geologists like myself do, and to teach classes to the next generation of geologists.
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| Mosaics in Marrakech, Morocco. |
This trip to Marrakech was for a conference of
sedimentologists, where this year’s theme was to bring terrestrial and planetary
scientists together to talk shop. Sedimentology is the study of rocks and the
sediments that are made up of parts of other rocks, chemically precipitated
rocks, and rocks that involve the help of animals to form at the Earth’s
surface. Sedimentology is also the study of the processes that form, transport,
and deposit the particles and chemicals that become part of sediments and
sedimentary rocks. Sediments and sedimentary rocks cover the majority of
Earth’s surface and are where most fossils are formed, preserved, and found. A
lot of processes that are involved in making sedimentary rocks are slow and
tedious, like the evaporation of a lake bed to form salts. Others involve the
slow settling of small particles on the seafloor. The reason I was invited to
this conference was that this meeting, the 32nd meeting of the International Association of Sedimentologists, had a special session on extreme
sedimentation, things that are bigger and faster than the sediments most people
think about.
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| Also I went to Morocco to eat all the couscous I could fit in my face. |
These extreme sediments form rapidly after the impact of a
meteorite, when a mountain collapses, when a tsunami rushes onshore, and, you
guessed it, when a volcano erupts explosively! Anything that is made up of discrete pieces of other rock get called clastic (from the Greek for "broken"), and then we can add modifiers to our hearts content. Deposits made by explosive
volcanic eruptions are made up of broken bits of rock, and we call them things like
pyroclastic (with a Greek prefix meaning "fire") when those particles are hot, or volcaniclastic when they are more
generically made up of things that needed a volcano to exist (bits of old lava and ash that were cold before becoming part of the new sediment). I study volcaniclastic rocks, mixtures of
rocks made from fresh rocks cooled from magma, old volcanic rocks that got
disrupted by more recent activity, and other rocks that were just in the way. The
way I describe these deposits is very similar to the way that a sedimentologist
would describe rocks formed by any other process that transports its ingredients at Earth's surface. The big difference is that most sedimentology works with
rocks that are emplaced in mostly horizontal beds, while volcanic rocks can
fill in valleys or be on steep slopes, as well as nice horizontal layers. We also
tend to use slightly different terms, but the principles are so similar the
name changes frequently seem silly (e.g. sand sized vs. ash sized).
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| Some volcaniclastic sediments from Frijoles Canyon, New Mexico. The biggest boulders in this image are about 50 cm across. You can see that the big block in the middle made a depression when it landed, we call it a sag. That means the block had to fly through the air ballistically to get there, that is pretty extreme. |
My contribution to the session was to talk about our explosion experiments at the University at Buffalo and how they have helped with the interpretation of
layered volcaniclastic rocks from explosive eruptions. There were 17 talks on a
range of processes that involved faster or even catastrophic deposition of
clastic rocks. These included meteorite impacts, glacial outburst floods, rock avalanches and turbidites (submarine flow of sediment that travels out into the deep ocean). Not only was it a great honor to be invited to talk in a series
like this, but also a really great chance to hear about a wide range of
specialties and see how much we can learn from research that initially doesn’t
sound anything like our own.
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| Talking about dynamite and volcanoes is one of the best parts of my job. |
The conference was hosted in a really neat building in the
new town area of Marrakech. The conference included an organized dinner
that took us all to the walled city (Medina) to stuff our faces on delicious Moroccan
food in a Riad. I was overwhelmed by all the architectural detail of the
building.
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I loved the mosaic work everywhere.
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| Look at all the details! |
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| The Riad in old town Morocco (the Medina). |
After the formal part of the conference, a group of us went
on a field trip to look at landscapes and rocks that are good
analogs for the surface of Mars. Mars has active aeolian (wind driven - from the Greek god of the wind, via Latin) processes
and evidence of ancient watery environments.
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| Sand ripples on Earth help inspire good conversations about how ripples and dunes form on Mars. |
Even though we were mainly looking for Mars analogs, Morocco
has so much awesome geology that we got distracted a few times. The Atlas
Mountains are a beautiful example of compressional tectonics having dramatic
folds and faults that make geologists drool. Some of the rock formations are so
photogenic that many other tourists recognize them from their photos.
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| Of course we stopped to look at the Pre-Cambrian stromatolites (some of the earliest evidence for life on Earth). |
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| Cool erosional features in the Anti-Atlas mountains. A friend of mine who went on a more traditional tourist trip tells me they are called the "Monkey Fingers." |
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| Vertical bedding, or rocks that were formed horizontally and then through tectonic forces (namely smashing of two continents together) they get deformed and, in this case, turned on end. |
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Devonian (350-400 million years old) sea critter remains (fossils) were abundant on our trip and a frequent distraction.
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| Excellent folds preserved in the Atlas Mountains. We spent much of the drive hanging out the windows to photograph the rocks. |
We then drove further out into the desert to experience wind
transport and deposition first hand. We played in dust storms, climbed dunes,
and drove over desert pavement.
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| Sand dunes in Erg Chebbi, Morocco. |
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Ventifacts, rocks sculpted by the wind dragging sand incessantly across its surface. The rock in the foreground is 2-3 cm thick.
Mud cracks in fine sand that formed as seasonal ponds between dunes dry up. The 10 Dirham coin is about 4 cm in diameter.
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This was my face post ~50 mph or 80 kph winds.
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| This is what my face looked like while still in those winds. I swear the camels laughed at us. |
The group we travelled with came from a variety of
backgrounds, including students through senior scientists that studied Earth, Titan, and
yes, Mars. We all learned a lot on the trip from the organizers as well as other
participants. Field trips of this sort are always a valuable way to get to see
rocks with local experts right next to you, but also to get a chance to
really get to know new colleagues in a way that is just not possible during the
hectic formal conference days.
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| After you share a dawn camel ride in a severe wind storm with someone you will remember them a lot more than if you just met briefly in a poster session. |
If you want to take a geological inspired tour of Morocco
there are lots of great suggestions (with coordinates) on the Ibn Battuta Centre website (named for the 14th century traveler of the same name from Morocco).
The center exists to help conduct field work in Morocco for geologists, rocket
scientists and everyone in between. They did a great job of making our field
trip possible and awesome.
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| If you get a chance to get to some of these spots in Morocco, it is also possible that you will run into packs of geologists staring at rocks. |
