#WaterfallWednesday Pic from today's walk to the wonderful Eas Dubh, east of Shiaba, in south Mull. Waterfall is maybe 25m high. Upper part of cliff is columnar basalt flow, lower part is a mixed sediment/volcaniclastic unit (both Palaeogene). Aslo a wee rainbow at the bottom 🌈 😊 #Mull#Geology#Waterfall#Rainbow
@rabenmutterschafft@riffreporter Da eine Erdepoche auf eine sehr lange Zeit angelegt ist, könnte man sich “Anthropos-“ als einen inklusiven Platzhalter für eine Entwicklung zum Besseren vorstellen, so hat das zumindest Paul Crutzen gesehen.
@37th_Division@riffreporter Ist in 3D schon heute viel mehr als eine dünne Schicht, von neuartigem Techno-Gürtel an Weltraumschrott über Millionen Kilometer Straßen, Tunnel, Bergwerke, dicke urbane Mischgesteine, bis hinab zu den Furchen aus Schleppnetzfischerei am Meeresboden, plus Enteisung der Polargebiete plus Artenverschleppung, Artensterben und massenhaft Nutztier- sowie Technofossilien, z.B..
#DogWalkingGeology Another loose rock from Ardalanish beach in SW Mull from this morning. This is a really distinctive rock, from the andesitic sills forming the lower part of the Glencoe volcanic sequence, 85km to the NE. Transported by glaciers. The purple alteration is partly hematite, but also distinctive pink manganese-rich epidote , which you can see in the core of the pale patch on the left of the cobble. #Geology#Mull#Glencoe
🤓 Fun Fact: these purplish altered Glencoe andesites are similar in colour, , chemistry and mineralogy to the famous Imperial Porphyry quarried by the Romans at Jabal Dokhan, in Egypt. I wonder if any of the Glencoe rocks might be carvable? https://www.dailyartmagazine.com/red-porphyry-symbol-of-imperial-power/
I've got some neat-o rock pix from near Death Valley. (Rock thread!)
These are from a pass will outside the park, between Chicago basin and Pahrump, NV. But this rock unit occurs in a remote part of Death Valley, too.
These particular rocks were float, not attached to bedrock.
This rock is part of a very old (>500 MYA) pre-Cambrian unit. It is pretty well silicified and has fractures filled in with more resistant minerals. They stand proud after erosion of wraker stuff.
Now I'm gonna show you a special kind of rock. It is called "my favorite rock right now".
(Every geologist has one. Everyone should have one.)
This rock is a mix of rougher grayish carbonate and more smooth buff-colored carbonate-cemented mudstone parts.
The carbonate is a mix of limestone and dolomite. Dolomite formation is funky. Happened way after limstone deposited. Wetting and drying with magnesium-rich fluids changed composition. Dolomite holds finer structures.
Let's take a closer look at that carbonate rock, especially the gray dolomite parts.
There is A LOT of fun detail in there. Zoom in close and check it out. Those little tiny channels are called microkarren. They form from super thin sheets of liquid (like dew) condensing and dissolving bits of rock as it creeps down due to gravity.
I'm looking for books/papers on the history and development of petrography and physical analog modeling of geologic structures. Anyone have recommendations? #geology
Here is an image of pyramid-like star dunes in the western part of Mesquite Dunes in Death Valley during a windstorm. These are accessible from the Mesquite Dunes parking area. It is usually pretty crowded.
But we are going to check out the far eastern area of Mesquite Dunes. There is a small parking area over there that is rarely visited. You can wander into the dunes and interdunes and find some especially interesting features....
Here is a picture of two crescent shaped barchanoid dunes in the E Mesquite sand dunes. The wind went from image right (S) to image left (N). The steep face indicates the downwind side.
There are smaller transverse ripples. The steeper face of the ripple also indicates downwind direction from image right to left.
Ripples are easier to make. They indicate most recent sand grain moving wind direction. Dunes are harder, they indicate a bigger wind that moved lotsa sand.
@Dtl That is genuinely fascinating, especially seeing where they decided to bore in areas you're familiar with. It's a deep topic... (I'll get my coat).
Update:
Some very interesting replies to this question
Kid asked very good question this morning: why is this fossil ammonite in a round concretion? As in how was it preserved? (I explained that in some locations you find roundish stones that when broken in half reveal a fossil ammonite or other fossil inside). But why do they form in these roundish shapes? What is the preservation method.
I no longer remember where this came from but I think, Whitby?
@Ruth_Mottram Concretions like this are wonderful 😊 . They preserve 3D fossils because they grow before the burial that might crush the fragile remains. I did this wee graphic for some similar ones (but which also show later "septarian" cracking). Your Whitby one grew like this, but for some reason, did not crack - maybe more complete mineralisation of bacterial slimeball? #Geology#Septarian#Diagenesis
Here is a detail of some of that salt deposit where the lake "went away".
(Can't use term "receded", because the lake might be bigger now. Maybe "moved away"?)
Wind was moving image left to image right. It swooped around the topographic obstacle. There is also a neat lumpiness repeating bump pattern as well. And on top of all this are the fine hairs of salt. Zoom in to image center for detail.
I think that this is an evaporative salt effloresecnce carved by wind.
@mike_malaska I get some of this fluff every winter near the threshold of my garage... but only on one side of the two car garage. Who put the salt there? 🤷♀️
Ok. Astrobiology in thise scene at Badwater, Death Vally
This looks lifeless and boring but...there is a massive microbial war happening beneath those waves.
Just at image right, during normal dry periods, there are three springs at Badwater. Each comes from different source waters and each has totally different chemistries, and totally different microbes that live in each spring. Normally they are seperate and never mix.