Tim Demko
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Tim Demko
@timdemko.xyz
After liking this post and reading the linked paper, I was keen to see if I'm missing these features in outcrops. Tooling around some basalt flows along Kona Coast in Hawaii today (Shoreline Park, just west of Kealakekua)...well, yep! Will be keeping my eye peeled for these in older flows in AZ!
October 6, 2025 at 6:48 AM
Any self-respecting ichnologist despises fish because they can make the most frustratingly uninterpretable traces.
www.livescience.com/63627-puffer...
October 3, 2025 at 10:11 PM
Here is the response from the event on my RaspberryShake 4D seismometer near Phoenix, AZ USA
September 13, 2025 at 4:18 AM
After poking around and finding the base of the flow, the story became much richer: the basalt had flowed over some eolian dunes which sourced the water for the hydrothermal system. The sand might have accumulated as obstacle dunes around a bedrock hill, then buried by the flow in a valley. (2/2)
September 9, 2025 at 3:57 AM
Saw these outcrops of the mineralized, brecciated top of a Miocene basalt flow today, evidence of an epithermal hydrothermal system. This indicates the interactions of mineralized, boiling water, explosively flashing to steam, breaking up the rock, depositing minerals in fractures and cavities (1/2)
September 9, 2025 at 3:57 AM
Joe's post reminded me of this piece of artwork given to me me by the artist, William "Rockman" Gooder from Duluth, MN. William would come to my office with collections of stones he chose from the gravel beaches of Lake Superior for his artwork, asking me to to tell him the story of each one. (1/2)
August 25, 2025 at 4:38 AM
MEGAQUAKE! 8.7 off of Kamchatka. Here is the response on my RaspberryShake 4D in Phoenix, AZ USA #earthquake #RaspberryShake
July 30, 2025 at 12:42 AM
July 20, 2025 at 2:18 AM
Here are some highlights from deep red Surprise, Arizona. There were several hundred folks lining about 4 blocks, both sides of the highway. Well behaved, except for a few drive-by hecklers. The group was very diverse, happy, and fired up! Kudos to the No Kings organizers!
June 15, 2025 at 4:56 PM
Thought of this photo right away: left it all in the field! Clockwise from left: Brian Bodenbender, me, Mark Uhen: Shell, WY, July 2004. We survived.
May 15, 2025 at 10:56 PM
Artificial Intelligence when I was a kid:
May 6, 2025 at 4:18 AM
Got an exclusive preview of the Auburn University Geo Explorer Lab, a 37 foot RV mobile learning lab under construction that will introduce students, teachers, and community partners to the breadth of geoscience approaches to science and social studies learning.
April 27, 2025 at 2:58 PM
What is the coolest shot in movies?

#Filmsky
February 15, 2025 at 5:07 AM
We did have a President who felt the same way: www.americanrhetoric.com/speeches/jim...
January 19, 2025 at 6:07 PM
< February 19 FTW >

We were both kissed by a rose on the grey...

This is fun, a timeline cleanse if you will. Who is your celebrity Birthday Twin, born on the same day as you?

Reply with a pic or gif
January 13, 2025 at 1:35 AM
These are crater-fill sediments in the Oligo-Miocene Hopi Buttes Volcanic Field. Volcanic rocks and volcanoclastic sediments interfinger with Bidahochi Formation. This succession preserves interaction between extrusive and intrusive igneous activity and a pre-Grand Canyon fluvial-lacustrine system.⚒️
January 9, 2025 at 7:28 PM
Saw this exposure of an extensional detachment fault today, capped by Quaternary sediments across an angular unconformity. Precambrian igneous rocks form the footwall, while Miocene volcanoclastics and basalt are in the hanging wall. The detachment is a fault zone, here expressed as 2 normal faults.
January 7, 2025 at 4:57 AM
Some great geomorphic and sedimentologic features seen while out mapping igneous/metamorphic rocks: feeder channels to the apex of this alluvial fan incised, left behind a flight of boulder-levee-lined terraces. Boulders were stranded along the channel edges by debris flows coming down the drainage.
December 14, 2024 at 10:30 PM
From a reply to a repost: didn't include because it doesn't have a scale. The contact here is much more complicated, but the big white crystals near the bottom of the pegmatite outcrop here are giant (1 m long) spodumene laths. You can spot other spodumene laths throughout the main pegmatite.
December 14, 2024 at 6:58 PM
Here is another nearby outcrop that I didn't include because it doesn't have a scale. The contact is much more complicated, but the big white crystals near the bottom of the pegmatite outcrop here are giant (1 m long) spodumene laths. You can spot other spodumene laths throughout the main pegmatite.
December 14, 2024 at 4:14 AM
Nice example of an igneous intrusive contact between a light colored pegmatite and a darker schist in central Arizona USA. The contact is sharp and sinuous, and the pegmatite shows little evidence of a finer-crystalline chilled margin. The pegmatite has abundant spodumene, a lithium-bearing mineral.
December 14, 2024 at 3:45 AM
Field work in the White Tank Mountains in central Arizona USA: great igneous relationships between screens or xenoliths of Proterozoic schist and a Cretaceous/Paleogene granite! There are also some younger pegmatite veins that cut both. This is also the lower plate of a metamorphic core complex.
December 7, 2024 at 5:12 AM
Found this impressive packrat midden in the Vulture Mountains of central Arizona USA. Packrats construct their middens by obsessively collecting vegetation debris and other objects within about 100 m of the midden site. They only get water from eating vegetation, so their urine is very concentrated
December 5, 2024 at 3:10 AM
A nice igneous intrusive relationship between a dark reddish brown andesite breccia and a light red rhyolite porphyry with dark mafic inclusions (left). This outcrop is part of the Vulture Mountains (right) volcanic center in central Arizona USA. These units were emplaced in the Miocene, ~20 Mya.
December 4, 2024 at 3:00 AM
"spoken-word-slam-poetry"...I knew someone would get the bit, eventually! Now, finally, you all know.
December 3, 2024 at 2:51 AM