100 days of geoscience
The career of an academic is filled with peaks and troughs. We have periods where we're rolling in grant funds, and then many years of no funding. We have high impact papers accepted with minor revisions, and then a string of rejections. And we have parts of the year where we are completely swamped with teaching and research, and then times between semesters where we have relative luxurious freedom to pursue our research interests...
It is perhaps needless to say that it was during the latter that the idea of a 100 day-long social media campaign came to me. In the past I have found that it is rarely wise to execute big ideas that originate during these periods of "free" time, since they are fleeting and valuable. Evidently I am not yet wise enough to listen to my own advice, and so, I plunged headfirst into a commitment to post a picture from my research once a day for 100 days, beginning on the first day of semester two, 2021.
✨100 days of geoscience✨ Through semester 2 I'm posting a geoscience picture every day that I've taken in the field or the lab. For the full explanation of each photo follow me on instagram (https://t.co/4R8n3AyygD) #100DaysofGeoscience @MonashEAE @Monash_Science @WOMEESA pic.twitter.com/Kxbs5Jz3NU
— Dr Melanie Finch (@melaniefinch_) July 25, 2021
I was somewhat mindful of how onerous this commitment could become, so before I launched the initiative I selected photos and pre-wrote 75 days worth of posts. I figured that with the awesome field work I had planned I would easily be able to come up with another 25 posts on the fly. Unfortunately, Victoria went into another lockdown shortly after #100daysofGeoscience started, so that put a swift end to my field work plans. I also found that once I saw the posts that people engaged with most, I ditched some of the planned posts and added new, different ones.
What did I learn? Scheduling is key and it is easy. Instagram and twitter both let you schedule many posts in advance. When I got very busy at the end of the semester (around day 70) I just pre-scheduled the rest of the posts through to day 100 so I wouldn't need to think about it. However, I would try to check in on my posts on twitter and instagram each day to answer people's questions and comments.
Even though this took a lot of time, I think I will do something like it again next year. A lot of people love geology as much as I do and it is awesome to be able to share my work with them. These are people who would not read or understand my papers, but who now see rocks in a different way. And that's what #100daysofgeoscience was all about.
100 | 90 | 80 | 70 | 60 | 50 | 40 | 30 | 20 | 10
100
Day 100: A subduction zone melange block in 3D. Blueschist and phengite schist interfolded, then folds rotated during shearing in the melange matrix. From Syros, Greece.
— Dr Melanie Finch (@melaniefinch_) November 1, 2021
#100DaysofGeoscience pic.twitter.com/RQiHRTWBAN
Day 99: Folds, faults and flanking folds in banded quartzite from Cap de Creus, N Spain.#100DaysofGeoscience pic.twitter.com/n3XZZJbFIj
— Dr Melanie Finch (@melaniefinch_) October 31, 2021
Day 98: Something scary for Halloween: ghost folds! Everything you can see is crystallised melt remnants except for the dark folded layers. These are schlieren (layers of residual biotite) that were folded in the sedimentary rock, probably before melting. #100DaysofGeoscience pic.twitter.com/yUej1pgySG
— Dr Melanie Finch (@melaniefinch_) October 30, 2021
Day 97: Mt Gumburanjun, NW Himalaya: a dome, formed by intrusions of melt into the country rock, as you can see in the second and third pictures which are close shots. #100DaysofGeoscience pic.twitter.com/YmiWN729Gz
— Dr Melanie Finch (@melaniefinch_) October 29, 2021
Day 96: A bubbling mud pool at Rotorua, New Zealand. Rain water percolates down through the rocks and mud, heats up and rises up to the surface in these bubbling mud pools. The rocks here are hot because there is magma within a few kilometres of the surface.#100DaysofGeoscience pic.twitter.com/2K17fJ9DEU
— Dr Melanie Finch (@melaniefinch_) October 28, 2021
Day 95: Porphyroclasts in ultramylonitic peridotite from the Finero complex, Italy under PPL (#1) and XPL (#2). On the bottom right of centre there is a grain with chessboard extinction. Other grains show kink bands, recrystallisation++#100DaysofGeoscience #thinsectionthursday pic.twitter.com/2DrKCJAoOi
— Dr Melanie Finch (@melaniefinch_) October 27, 2021
Day 94: Leucocratic layer displaced by shear zones in granodiorite zoomed out (photo 1) and close up (photo 2).#100DaysofGeoscience pic.twitter.com/nUl8mfzqpA
— Dr Melanie Finch (@melaniefinch_) October 26, 2021
Day 93: Zooming into folds rotated into a shear zone (image one is zoomed out and shows shear zone, image two is closer in, image three shows folds). From Cap de Creus, N Spain.#100DaysofGeoscience pic.twitter.com/1OEltnxdGY
— Dr Melanie Finch (@melaniefinch_) October 25, 2021
Day 92: Sunset over Eldee station in the Australian outback near Broken Hill, far west NSW#100daysofgeoscience pic.twitter.com/qOaIhh7myM
— Dr Melanie Finch (@melaniefinch_) October 24, 2021
Day 91: The brown layer here with the dark boundary is a pseudotachylyte within a mylonite. The mylonite formed in the hanging wall of a high temperature thrust shear zone and as the hanging wall moved upwards it cooled and brittle structures formed.#100DaysofGeoscience pic.twitter.com/58Um18BlM7
— Dr Melanie Finch (@melaniefinch_) October 23, 2021
90
Day 90: Thin section image in PPL of isoclinal folds (hooks) in an orthogneiss. It is easy to imagine the folds were once joined together and have been sheared apart. #100DaysofGeoscience pic.twitter.com/Z4zMPMaRgO
— Dr Melanie Finch (@melaniefinch_) October 22, 2021
Day 89: Folded leucocratic layer in a mylonite. I spent a long time staring at this outcrop! There are a lot of different shear sense indicators#100DaysofGeoscience pic.twitter.com/FbLmGk7Opz
— Dr Melanie Finch (@melaniefinch_) October 21, 2021
Day 88: A garnet porphyroblast with phengite in pressure shadows and on the edges, within a epidote-blueschist. From Syros, Greece.#ThinsectionThursday #100DaysofGeoscience pic.twitter.com/sK5NSTiguX
— Dr Melanie Finch (@melaniefinch_) October 20, 2021
Day 87: Migmatite (rock with layers) with a melt escape channel (diagonal layer from bottom centre to top right). Channels like these allow melt to migrate out of migmatites. Different channels can link up and ultimately melt can end up in large plutons #100DaysofGeoscience pic.twitter.com/BrgDiODe1d
— Dr Melanie Finch (@melaniefinch_) October 19, 2021
Day 86: Folding in marble adjacent to apparently undeformed psammite in Cap de Creus, N Spain#100DaysofGeoscience pic.twitter.com/mTSKwYxG5e
— Dr Melanie Finch (@melaniefinch_) October 18, 2021
Day 85: A feldspar sigma clast with inclusions of tourmaline in a mylonite. Note the higher strain at the margins of the clast.#100DaysofGeoscience pic.twitter.com/B1Up91VXGV
— Dr Melanie Finch (@melaniefinch_) October 17, 2021
Day 84: Deformed layers of garnet melanosome and leucosome remnants in a mylonitic migmatite from Sierra de Quilmes.#100DaysofGeoscience pic.twitter.com/IOJG4bBeJn
— Dr Melanie Finch (@melaniefinch_) October 16, 2021
Day 83: Leucocratic layer displaced by shear zones zoomed out (photo 1) and close up (photo 2). Cap de Creus, N Spain#100DaysofGeoscience pic.twitter.com/JHJluII5sA
— Dr Melanie Finch (@melaniefinch_) October 15, 2021
Day 82: Sheared calc-silicate pod. The red spots in the centre are mostly grossular garnet, the pale layer is epidote and the green is amphibole. #100DaysofGeoscience pic.twitter.com/NLGEJHEUka
— Dr Melanie Finch (@melaniefinch_) October 14, 2021
Day 81: Exsolution lamellae of garnet in pyroxene in mantle xenolith. The garnet exsolutions have kelyphite on their edges - fine-grained mineral intergrowth that forms due to quick metamorphic grade changes.#Thinsectionthursday #100daysofGeoscience pic.twitter.com/U3i5ksrWYR
— Dr Melanie Finch (@melaniefinch_) October 13, 2021
80
Day 80: Mylonite with stretched leucocratic layer and sigma clasts. From this it is easy to imagine how sigma clasts form - starting out as longer leucocratic layers which are thinned and recrystallised during shearing, leaving only a few isolated clasts.#100DaysofGeoscience pic.twitter.com/qCM0rQhzv5
— Dr Melanie Finch (@melaniefinch_) October 12, 2021
Day 79: Folded pegmatite. The wavelength of the folds changes with the thickness of the pegmatite layer - thinner layers have shorter wavelengths. From Cap de Creus, Spain#100daysofgeoscience pic.twitter.com/UVR1fALpBb
— Dr Melanie Finch (@melaniefinch_) October 11, 2021
Day 78: On our trek through the Himalaya we had the help of a local guide named Stopel. This is his house, where he kindly hosted us for a night and made us the most delicious Momos (Tibetan dumplings) that I have ever eaten #100DaysofGeoscience pic.twitter.com/WOFfhPvvWe
— Dr Melanie Finch (@melaniefinch_) October 10, 2021
Day 77: Mylonite with sigma and delta clasts and stretched leucocratic layers.#100DaysofGeoscience pic.twitter.com/E1ZcaPOCNc
— Dr Melanie Finch (@melaniefinch_) October 9, 2021
Day 76: Metre scale C' shear bands at Cap de Creus (look for lens cap for scale, right of centre)#100DaysofGeoscience pic.twitter.com/uqj3V5WQz8
— Dr Melanie Finch (@melaniefinch_) October 8, 2021
Day 75: The lens cap is on a layer that is mostly cordierite. It used to be a pelite and underwent partial melting. Melt was extracted and left behind this cordierite-rich melanosome #100DaysofGeoscience pic.twitter.com/tQi1kJqGvq
— Dr Melanie Finch (@melaniefinch_) October 7, 2021
Day 74: A cross polarised image down a microscope of a protomylonite. The larger more round clasts are feldspar, the long ribbons are quartz, and the fine matrix is biotite, muscovite, feldspar and quartz. This image is about 2 cm long.#100DaysofGeoscience #thinsectionthursday pic.twitter.com/VhG3iiFXKp
— Dr Melanie Finch (@melaniefinch_) October 6, 2021
Day 73: Asymmetric folds indicating dextral shearing in a tourmaline pegmatite from Sierra de Quilmes, NW Argentina.#100DaysofGeoscience pic.twitter.com/TMyoQgHGvP
— Dr Melanie Finch (@melaniefinch_) October 5, 2021
Day 72: A village in the Zanskar Himalaya. Can you spot all the solar panels on the roofs of the houses? No poles and wires out here.#100daysofgeoscience pic.twitter.com/8UqpEIwexU
— Dr Melanie Finch (@melaniefinch_) October 4, 2021
Day 71: Pegmatite (layer width~4m) offset by dextral shear zone at Cap de Creus, N Spain.#100DaysofGeoscience pic.twitter.com/TdQkPDdvMX
— Dr Melanie Finch (@melaniefinch_) October 3, 2021
70
Day 70: Isoclinally folded calc-silicate pod. The red layer in the centre is mostly grossular garnet, the pale layer is epidote and the green is amphibole. #100DaysofGeoscience pic.twitter.com/SLQHnMnpTt
— Dr Melanie Finch (@melaniefinch_) October 2, 2021
Day 69: A tale of two viscosities. Psammite (bottom) shows brittle fracture while marble flows. From Cap de Creus, N Spain#100DaysofGeoscience pic.twitter.com/xHFR6w6dMU
— Dr Melanie Finch (@melaniefinch_) October 1, 2021
Day 68: The horizontal, pink-grey layer is the crystallised remnants of melt that was flowing out of the rock, towards the right. The striped rock (top and bottom) is stromatic migmatite. Melt migrated from the migmatite toward the horizontal channel #100DaysofGeoscience pic.twitter.com/F1RD1mFKTH
— Dr Melanie Finch (@melaniefinch_) September 30, 2021
Day 67: Partially recrystallised porphyroclast in an ultramylonitic peridotite from the Finero complex, Italy under cross polarised light. #100daysofgeoscience #thinsectionthursday pic.twitter.com/QNfxJJVU44
— Dr Melanie Finch (@melaniefinch_) September 29, 2021
Day 66: Can't beat this for an office. One of our field work days in Syros, Greece was spent at the north of the island where off into the distance you could see the next island over, Mykonos. #100DaysofGeoscience pic.twitter.com/9dmwzXSHur
— Dr Melanie Finch (@melaniefinch_) September 28, 2021
Day 65: Folds in a banded quartzite from Cap de Creus, N Spain
— Dr Melanie Finch (@melaniefinch_) September 27, 2021
#100DaysofGeoscience pic.twitter.com/QsLRGk3E0G
Day 64: There is a river at the foot of the mountain in the background and you can see here the rocks that make up its banks. Huge boulders are transported during periods where the river flows quickly, perhaps during monsoon season in the NW Himalaya #100DaysofGeoscience pic.twitter.com/Eiy1X4hBzb
— Dr Melanie Finch (@melaniefinch_) September 26, 2021
Day 63: I don't think "comet" porphyroclasts are an accepted term in structural geology, but this is an example of one. I'm not sure exactly how these form and I've only ever seen this one. This is in a mylonite from the Pichao shear zone NW Argentina #100daysofgeoscience pic.twitter.com/zlc0WUJmww
— Dr Melanie Finch (@melaniefinch_) September 25, 2021
Day 62: S-C-C' fabric in a serpentinite from Rocca Canavese, Turin, Italy. Anisotropic rocks make the best fabrics 🤩#100daysofgeoscience pic.twitter.com/dkcwWalN0z
— Dr Melanie Finch (@melaniefinch_) September 24, 2021
Day 61: Foliated eclogite facies metagranodiorite (white-grey) cut by undeformed andesite dykes with plagioclase phenocrysts and chilled margins, from Valle d'Aosta, Sesia Zone, Italy. #100daysofgeoscience pic.twitter.com/R77mUanJtl
— Dr Melanie Finch (@melaniefinch_) September 23, 2021
60
Day 60: Garnet with rims of kelyphite: corona with intergrowth of multiple phases (spinel, pyroxenes). Garnet peridotite rapidly decompressed as xenolith in basalt, moved from the garnet stability field to spinel stability field, causing partial retrogression #100DaysofGeoscience pic.twitter.com/kAk7HO3LAO
— Dr Melanie Finch (@melaniefinch_) September 22, 2021
Day 59: A block of country rock with folds (right, schollen) abruptly cross-cut by a rock without folds or fabric (left, crystallised melt). The boundary between metamorphic diatexites and igneous rocks is certainly a fuzzy one #100DaysofGeoscience pic.twitter.com/3bFWAgMj68
— Dr Melanie Finch (@melaniefinch_) September 21, 2021
Day 58: Lia Beach, Syros, Greece. I wasn't sure whether to collect amazing blueschist and eclogite pebbles or go for a dip after a long hike. The green rocks in the outcrop on the right are serpentinites and chlorite schists, matrix to the subduction channel #100DaysofGeoscience pic.twitter.com/TrBRiTk6er
— Dr Melanie Finch (@melaniefinch_) September 20, 2021
Day 57: This is for the Aussie geologists missing field work, many of you would recognise this creek bed. Over the years many unis have run mapping courses on Eldee station near Broken Hill. Even after many trips, you still learn something new each time #100DaysofGeoscience pic.twitter.com/Hb3CCHWqNk
— Dr Melanie Finch (@melaniefinch_) September 19, 2021
Day 56: A melange! Here there are eclogites (green and red) mixing into the carbonate matrix. This is rock hybridisation in action! From Syros, Greece, just underneath the Vari Detachment.#100daysofgeoscience pic.twitter.com/vHJyospRkr
— Dr Melanie Finch (@melaniefinch_) September 18, 2021
Day 55: A mylonitic granite. I wonder if the rectangular porphyroclasts started as a longer leucocratic layer that boudinaged into pieces…? Or can rectangular porphyroclasts from naturally from granitic phenocrysts? Any ideas? #100daysofgeoscience pic.twitter.com/K8DFFPt6JP
— Dr Melanie Finch (@melaniefinch_) September 17, 2021
Day 54: A valley in the Zanskar Himalaya, NW India. We camped near this house and in the morning loaded the donkeys back up to continue along the valley. I watched the moon rise above these mountains the night before and it was quite wonderful. #100DaysofGeoscience pic.twitter.com/sinl3RXTrU
— Dr Melanie Finch (@melaniefinch_) September 16, 2021
Day 53: Green mineral is omphacite, blue is glaucophane. In the centre is jadeite (probably after omph) that fractured into pieces and the pieces have sheared apart and rotated. Syros, Greece #100DaysofGeoscience #ThinSectionThursday pic.twitter.com/FWprYlrXQt
— Dr Melanie Finch (@melaniefinch_) September 15, 2021
Day 52: When starting out in research I was so eager to become a structural geologist, I forgot why I got into geology originally. Teaching general 1st year geology this year reminded me how awesome the whole of geology is, including sand dunes like these #100DaysofGeoscience pic.twitter.com/v0MIR8OmJT
— Dr Melanie Finch (@melaniefinch_) September 14, 2021
Day 51: Migmatite formed after interbedded psammite (left) and pelite (right). Melt escaping along the light-coloured channel (diagonal from the bottom right corner). At the metapsammite the channel branches because the higher competence inhibits migration. #100DaysofGeoscience pic.twitter.com/7Pn8HVTicq
— Dr Melanie Finch (@melaniefinch_) September 13, 2021
50
Day 50: A brecciated blueschist. Fluid infiltrated the rock, which increased the pressure and caused fracturing. Metasomatism caused growth of hydrous minerals (phengite and epidote). The hammer is about 70 cm long. #100DaysofGeoscience pic.twitter.com/EBpkdF7ila
— Dr Melanie Finch (@melaniefinch_) September 12, 2021
Day 49: Quartz veins in metapsammite and metapelite. My interpretation: qtz veins formed at high angle to bedding, shortened ~perpendicular to bedding, stronger psammite layer deformed less than the weaker pelitic layer, Qtz veins transposed in pelite only #100DaysofGeoscience pic.twitter.com/UTYffSKi3K
— Dr Melanie Finch (@melaniefinch_) September 11, 2021
Day 48: Shyok river valley and the Karakoram range in the background (NW India). Close to the suture between the Indian and Eurasian tectonic plates, we stood here and looked north, picturing the huge tectonic forces that had played out over millions of years #100DaysofGeoscience pic.twitter.com/LMOXrHEOwu
— Dr Melanie Finch (@melaniefinch_) September 10, 2021
Day 47: A mylonitised Grt-migmatite (this rock grades into less deformed rocks that show evidence of partial melting). Note change in grain size and porphyroclast proportion from the top of the photo (mylonite) to the bottom (ultramylonite). #100DaysofGeoscience pic.twitter.com/D8wqjFeamf
— Dr Melanie Finch (@melaniefinch_) September 9, 2021
Day 46: Ultramylonitic peridotite (Finero complex, Italy). Porphyroclasts show deformation bands, lamellae, kinking and recrystallisation. The ultramylonitic matrix is olivine, pyroxenes, phlogopite, spinel. #100DaysofGeoscience #thinsectionthursday pic.twitter.com/1bBJ9LTYoy
— Dr Melanie Finch (@melaniefinch_) September 8, 2021
Day 45: An outcrop from the valley in yesterday's photo. This is a blueschist block in orthogneiss from Valle d'Aosta, Sesia Zone, Italy. #100daysofgeoscience pic.twitter.com/lnYSwoZCoL
— Dr Melanie Finch (@melaniefinch_) September 7, 2021
Day 44: Valle d'Aosta, Sesia Zone, Italy, a 100 km-long valley in the Western Alps, carved by glaciers. The valley reveals continental crust that underwent multiple metamorphic cycles incl. subduction to eclogite facies, pretty rare for buoyant crustal rocks. #100DaysofGeoscience pic.twitter.com/zrx8BZyPKI
— Dr Melanie Finch (@melaniefinch_) September 6, 2021
Day 43: Garnet-blueschist (Syros, Greece) with much more garnet than any other blueschists we saw. Why so much garnet here and not in other nearby rocks? Perhaps a different composition - more Al or Mn? Sorry for the shadows - bad photo but great outcrop. #100DaysofGeoscience pic.twitter.com/9oLvYkT19R
— Dr Melanie Finch (@melaniefinch_) September 5, 2021
Day 42: This garnet-blueschist from Syros in Greece has been metasomatised, forming layers of epidote (orangey cream colour). The huge clast in the bottom right is also epidote and has been asymmetrically sheared and rotated. #100DaysofGeoscience pic.twitter.com/GeWmdcebOV
— Dr Melanie Finch (@melaniefinch_) September 4, 2021
Day 41: Cordierite (purple) and garnet in a leucosome of a migmatite. In the centre there is a couple of grains of cordierite with a garnet rim!#100DaysofGeoscience pic.twitter.com/myyXR2ibmW
— Dr Melanie Finch (@melaniefinch_) September 3, 2021
40
Day 40: Orthogneiss thin section (XPL) showing coeval brittle and ductile processes. Large fractured feldspar porphyroclast on the right. The matrix is quartz, feldspar, muscovite and biotite and flows around the clasts, forming S-C-C' fabric #100DaysofGeoscience pic.twitter.com/gVaqA83DQv
— Dr Melanie Finch (@melaniefinch_) September 2, 2021
Day 39: I use this thin section in teaching and it is tricky for students because all the minerals are ~colourless in PPL, so it forces them to use other mineral properties. There is zoisite, amphibole, phengite, omphacite, quartz and garnet: an eclogite#100DaysofGeoscience pic.twitter.com/kC4h6yRCY6
— Dr Melanie Finch (@melaniefinch_) September 1, 2021
Day 38: Interbedded psammite (metamorphosed sandstone) and pelite (metamorphosed mudstone) with cordierite porphyroblasts in the pelitic layers only. Cordierite contains aluminium, which is in low quantities in psammites, preventing Crd growth in these layers #100DaysofGeoscience pic.twitter.com/IZKlBL8QVT
— Dr Melanie Finch (@melaniefinch_) August 31, 2021
Day 37: This tiny dyke is in a mylonite. The tips of the dyke have been asymmetrically sheared so they step up to the right, indicating dextral shear. #100DaysofGeoscience pic.twitter.com/RsYHexoYdp
— Dr Melanie Finch (@melaniefinch_) August 30, 2021
Day 36: Salinas Grandes in North Argentina. This region is a desert and the salt flats formed about 12,000 years ago when a huge lake evaporated.#100DaysofGeoscience pic.twitter.com/PktQEztdgi
— Dr Melanie Finch (@melaniefinch_) August 29, 2021
Day 35: The green layers are calc-silicate and the brown layers are sandstone. Sandstones are mostly quartz and feldspar, which recrystallise during deformation, whereas calc-silicates are stronger and shear into asymmetric shapes and sigma-type objects. #100DaysofGeoscience pic.twitter.com/AqXRPlsQzz
— Dr Melanie Finch (@melaniefinch_) August 28, 2021
Day 34: S-C-C' fabric in an orthogneiss in the Zanskar shear zone, NW Himalaya. I took this photo in 2013 - flash forward 7 years and I would become low-level obsessed with C' shear bands and write a whole paper about how they form🤩#100DaysofGeoscience pic.twitter.com/cqHl8NipPc
— Dr Melanie Finch (@melaniefinch_) August 27, 2021
Day 33: To teach a field course in Cap de Creus would be an absolute dream! Check out this isoclinal fold with an intersection lineation you can measure from metres away!#100daysofgeoscience #FoldFriday pic.twitter.com/65eQpiQROM
— Dr Melanie Finch (@melaniefinch_) August 26, 2021
Day 32: Delta clast in ultramylonite under cross polarised light. The clast is partially recrystallised and the tail on the right boudinaged and recrystallised. The left tail is completely recrystallised. Image length ~ 3 cm. #100DaysofGeoscience #thinsectionthursday pic.twitter.com/8u6twTwdKo
— Dr Melanie Finch (@melaniefinch_) August 25, 2021
Day 31: The lighter layers in this migmatite are remnants of crystallised melt. They are folded and also appear on the axial plane of the folds. During shortening, pore spaces in the rock align in bands perpendicular to shortening and melt migrates into them#100DaysofGeoscience pic.twitter.com/NDjW2COakx
— Dr Melanie Finch (@melaniefinch_) August 24, 2021
30
Day 30: Pink granite in the hills of Sierra de Quilmes, NW Argentina. I'm usually all about the outcrop or micro-scale detail so I often forget to take shots like this but they are very useful in talks for giving context. Plus, the cacti really set the mood. #100DaysofGeoscience pic.twitter.com/AvXPC0HGhq
— Dr Melanie Finch (@melaniefinch_) August 23, 2021
Day 29: Champagne pool from 'Wai-o-tapu Thermal Wonderland' in New Zealand. Magma deep under the surface heats water to ~300°C, which circulates and dissolves metals. At the surface arsenic and antimony sulfides precipitate, including orange orpiment#100daysofgeoscience pic.twitter.com/kPHtO5rgiS
— Dr Melanie Finch (@melaniefinch_) August 22, 2021
Day 28: Delta clast in ultramylonite from Sierra de Quilmes, NW Argentina. It's hard to believe this rock started out as a granite! With hard work, determination, and a lot of strain, even the most common igneous rock can one day become a beautiful mylonite. #100DaysofGeoscience pic.twitter.com/94tf8SISGm
— Dr Melanie Finch (@melaniefinch_) August 21, 2021
Day 27: Lawsonite (white) in a garnet blueschist from Syros, Greece. Lawsonite is pretty rare in the geological record even though it is stable over a wide P/T range. It retrogresses easily so rocks need to be exhumed quickly for it to be preserved #100DaysofGeoscience pic.twitter.com/FqXH2wR2B5
— Dr Melanie Finch (@melaniefinch_) August 20, 2021
Day 26: A melanosome in a migmatite (partially melted rock). When a rock melts the more Si-rich, felsic minerals melt first and can flow away leaving behind Fe- & Mg- rich dark minerals, like garnet (red) and cordierite (purple) in the melanosomes. #100DaysofGeoscience pic.twitter.com/WKD1S6RDnJ
— Dr Melanie Finch (@melaniefinch_) August 19, 2021
Day 25: Garnet amphibolite from Broken Hill, Australia. In PPL green mineral is hornblende, white is plagioclase or quartz and the light brown hexagon in the middle is garnet. Partial replacement of garnet by hornblende on the lower left #100DaysofGeoscience #ThinSectionThursday pic.twitter.com/iGoBr7N36t
— Dr Melanie Finch (@melaniefinch_) August 18, 2021
Day 24: In the Himalaya we drove from Leh to Zanskar on the first day the roads opened after a period of heavy snow. There were lots of other cars doing the same. Just outside Rangdum we were stuck in traffic so I jumped out and captured this photo. #100DaysofGeoscience pic.twitter.com/lVXHV4fs4x
— Dr Melanie Finch (@melaniefinch_) August 17, 2021
Day 23: It's rare to get a good photo of a sheath fold but Cap de Creus (Spain) delivers again. These folded quartz veins stick out because they are resistant to weathering. The fold on the right has an extended, conical nose = a sheath fold. #100DaysofGeoscience pic.twitter.com/EgcFuR0Y7z
— Dr Melanie Finch (@melaniefinch_) August 16, 2021
Day 22: The light-coloured vertical layer is crystallised melt. On either side you can see horizontal layers of crystallised melt. What do you think geos - is the vertical band feeding the horizontal layers, or are the horizontal layers feeding the vertical? #100DaysofGeoscience pic.twitter.com/VwwV9gQoVZ
— Dr Melanie Finch (@melaniefinch_) August 15, 2021
Day 21: This is a diatexite, a rock that melted so much it lost coherence. The dark layers (biotite) are called schlieren, which are remnants of the original sedimentary rock. The schlieren folded close to the lighter rock during magma flow.#100daysofgeoscience pic.twitter.com/z1Z8NfIU2L
— Dr Melanie Finch (@melaniefinch_) August 14, 2021
20
Day 20: Folded layers of jadeitite (grey), blueschist (blue) and actinolitite (black). Jadeitite layers form in subduction channels when fluids interact with (metasomatise) eclogites, blueschists or serpentinites. From Syros, Greece.#100daysofgeoscience pic.twitter.com/TzR51Icngg
— Dr Melanie Finch (@melaniefinch_) August 13, 2021
Day 19: Zoom in and you might be able to see tails wrapped around this large feldspar porphyroclast as a result of rotation of the clast in the mylonite (grey rock) during shearing. From Sierra de Quilmes, NW Argentina.#100DaysofGeoscience pic.twitter.com/gVnR1PGxlw
— Dr Melanie Finch (@melaniefinch_) August 12, 2021
Day 18: This is a synchrotron image with titanite (pink), muscovite (green), lawsonite (blue) and glaucophane (black). Lawsonite veins were folded then limbs and hinges were sheared apart. Port Macquarie, Australia, photo width=3 mm. #100DaysofGeoscience #thinsectionthursday pic.twitter.com/zqqd1gMVi9
— Dr Melanie Finch (@melaniefinch_) August 11, 2021
Day 17: Serpentinite looks so awful in thin section so it has never been my favourite but even haters have got to agree that it forms spectacular folds. Chevron (pointy) folds only form in weak, anisotropic rocks like serpentinite. From Rocca Canavese, Italy #100daysofgeoscience pic.twitter.com/IDn5thPVrD
— Dr Melanie Finch (@melaniefinch_) August 10, 2021
Day 16: Garnet-epidote blueschist from Syros, Greece. this is another cool example of mineral strength controlling deformation. Epidote (cream) is strong and forms asymmetrically-sheared clasts while glaucophane (blue) wraps around it. #100DaysofGeoscience pic.twitter.com/DhkEZsHWoH
— Dr Melanie Finch (@melaniefinch_) August 9, 2021
Day 15: This is a photo from the drive from Leh to Diskit in the NW Himalaya. We were driving north to find the suture zone between the Indian and Asian continental plates: the exact place where the two plates collided ~50 million years ago. #100DaysofGeoscience #Himalaya pic.twitter.com/VqIKY8zGwH
— Dr Melanie Finch (@melaniefinch_) August 8, 2021
Day 14: Granitoid (bottom) to gneiss (middle) to mylonite (top) over a few centimetres. The rock was originally all granitoid but the top bit was deformed, which stretched and recrystallised the minerals. Another fine example from Cap de Creus, N Spain #100DaysofGeoscience pic.twitter.com/jfVJjUFlDv
— Dr Melanie Finch (@melaniefinch_) August 7, 2021
Day 13: This is the ideal situation for a structural geologist: a shear zone with clear boundaries that offsets a marker (the cream coloured dyke) allows for easy calculation of strain and displacement. From Cap de Creus, N Spain. #100DaysofGeoscience pic.twitter.com/zr3xFMjOEz
— Dr Melanie Finch (@melaniefinch_) August 6, 2021
Day 12: When we found this rock in the field we didn't know what it was. The key to understanding it was walking away from it - gradually the proportion of white crystals increased until we found a granite. This is an ultramylonite - a very deformed granite #100DaysofGeoscience pic.twitter.com/Ar5FdlLiW4
— Dr Melanie Finch (@melaniefinch_) August 5, 2021
Day 11: Garnet porphyroblast (pink) with quartz (clear) and biotite (brown) inclusions in a schist from Broken Hill, NSW, Australia. Inclusions are aligned and continuous with the external foliation, indicating garnet is post-tectonic #100DaysofGeoscience #thinsectionthursday pic.twitter.com/0YqQIx8yTi
— Dr Melanie Finch (@melaniefinch_) August 4, 2021
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Day 10: Folded "mega-porphyroclasts" from a subduction channel in Syros, Greece. This rock consists of layers of blueschist and phengite schist (white) that have behaved as a strong block and folded within the weak shear zone matrix. #100DaysofGeoscience pic.twitter.com/RdSt4hGYSo
— Dr Melanie Finch (@melaniefinch_) August 3, 2021
Day 9: It blew my mind the first time I saw crystals as big as my head! This is a pegmatite: a very coarse-grained felsic igneous rock that crystallises from water-rich magma. The water allows huge crystals to grow. From Broken Hill, NSW, Australia #100DaysofGeoscience pic.twitter.com/seMvfa7kyP
— Dr Melanie Finch (@melaniefinch_) August 2, 2021
Day 8: Orthogneiss from the Zanskar shear zone, NW Himalaya. The asymmetrically sheared leucocratic layers indicate normal shearing, which is unexpected during continent collision. This shear zone stretches 1000's of kms and cuts through Mt Everest! #100DaysofGeoscience #Himalaya pic.twitter.com/VSkklTEPo2
— Dr Melanie Finch (@melaniefinch_) August 1, 2021
Day 7: Coming from the relative flat expanse of Australia it was pretty amazing to see the Himalaya for the first time. I had never seen mountains before and these are Earth's best. This photo is on our first day in Leh, Ladakh, before beginning field work #100DaysofGeoscience pic.twitter.com/jVZgtkPljc
— Dr Melanie Finch (@melaniefinch_) July 31, 2021
Day 6: Brilliant example of rock strength causing strain partitioning. We think of ductile and brittle structures as occurring at different places in the crust but there are lots of examples where they occur concurrently due to rheology contrast or fluids #100DaysofGeoscience pic.twitter.com/3owf9bIlYJ
— Dr Melanie Finch (@melaniefinch_) July 30, 2021
Day 5: Extreme strain partitioning! The black/white marble partitions strain because it is weaker than the brown psammite. Within the marble, a thin layer of psammite folds, but psammite layers above and below appear undeformed. From Cap de Creus, Spain #100DaysofGeoscience pic.twitter.com/y7ypDbZ9Cj
— Dr Melanie Finch (@melaniefinch_) July 29, 2021
Day 4: Partial melting textures in thin section! Films of quartz surround peritectic cordierite, orthopyroxene and tabular plagioclase, which crystallised first in the melt. Go to my instagram for the full explanation https://t.co/LJ3bB5H2J3 #100DaysofGeoscience pic.twitter.com/gvJPyRizLu
— Dr Melanie Finch (@melaniefinch_) July 28, 2021
Day 3: A stromatic metatexite is a #migmatite (partially melted rock) that is stripey, made up of alternating light and dark layers. The light layers are crystallised melt (leucosomes) and here contain big garnets and orthopyroxene (peritectic minerals). #100DaysofGeoscience pic.twitter.com/3DpplRwEoY
— Dr Melanie Finch (@melaniefinch_) July 27, 2021
Day 2: I am irrationally fond of what happens to compositional layering during metamorphism. Here we see a reversal in relative grain size due to metamorphism: fine-grained mudstone became coarse garnet-mica schist whereas boring sandstone just recrystallised #100DaysofGeoscience pic.twitter.com/17RZ1WK9l2
— Dr Melanie Finch (@melaniefinch_) July 26, 2021
Day 1: Tectonic mixing in subduction channel melange (#Syros, Greece). Eclogite (green and red rock) is stronger than surrounding carbonate, so it resists the deformation while the carbonate happily flows around it. #100DaysofGeoscience @MonashEAE pic.twitter.com/T04q06EZiB
— Dr Melanie Finch (@melaniefinch_) July 25, 2021