Please LIKE and SUBSCRIBE. I also appreciate your continual support of these geology education videos. To do so, click on the "Thanks" button just above (right of Download button) or by going here: www.paypal.com/donate/?hosted_button_id=EWUSLG3GBS5W8 Or: www.buymeacoffee.com/shawnwillsey
Fairbanks, Alaska with its tundra - would have its own frost wedging with the permafrost melting and refreezing above the bedrock and the organic layers. But, the biggest frost wedging, as in rock cracking, would be in the mountains (Rocky Mountains) of Wyoming and high deserts like Colorado and Nevada.
It was seeing pictures of these amazing rock formations as a child that fascinated me and it is great to learn more about the Earth now I'm retired and have time. Thanks for another informative episode, Shawn. I am learning so much and keeping my brain active.
You truly have the heart of a teacher. I learn from you. While I try to view your many varied videos I especially like your work on Yellowstone and Island Park (Henry's fork etc). Last June I went to the parking area near Harriman State Park off US20 where you did a video. Thanks for what you do.
The comparison of the 1888 tomb stones is, I think flawed. I would bet you that both these graves were marked with marble and the one that is granite had its eroded marble headstone replaced with granite sometime in the last 50 years. It is true that the granite is much longer lived than marble in this application. It was just not very common in 1888 to haul heavy granite long distances for grave markers and the style is also more common of 20th century markers.
That’s curious. I would have thought that weathering would be a subset of erosion, not a separate category. How is it determined that exfoliation is due to expansion, rather than small amounts of water taking advantage of weakness in the rock? Can expansion be measured to verify internal expansion leads to outer exfoliation?
Great session as ever. Anomalous expansion of water just below freezing point (-4°C I think) is what bursts open steel water pipes in winter.. Plumbers nightmare.
No, I don't think that's correct. The anomalous expansion of water is as you cool it below about +4C, and it's because the molecules start to arrange in an ice-like way. Pipes crack because there's further expansion as water freezes, but ice can't flow out of the way like liquid water can. Below freezing, ice contracts as it cools, just like anything else -- because the molecules are vibrating less so pack closer together.
OK. I've done my part - I've liked and subscribed. Now it's your turn - please add this video to the GEOL 101 Playlist (which, I am very happy to see, is now in first-to-last order!👍) 🙂
So interesting! Great lesson. I never thought of erosion and weathering as different processes before. Question - why is salt weathering considered a physical process and not a chemical one? Just curious! Thanks for taking the time to put these sessions together and teach us!!
Understanding how water can flow in cracks, and then when it turns into ice - it becomes a massive atomic force in molecular expansion, and cracking the hardest of rock strata. H2O ... or 2 parts Hydrogen atoms (2 x +1) to 1 part Oxygen atom (-2), ... has the Hydrogen atoms locked to the Oxygen atom, but separated by 104.5 degrees. Active and free flowing water molecules flow all over the place, yielding no specific structure except that it is technically a flow metal gas. Approaching 0 C (32 F), the transition state of liquid water turning into ice, there is the actual contraction of water volume, as the H2O molecules align, and fall together into a massive military-like battalion of soldier Hydrogens and Oxygens. The water molecules align in strings along the X-axis, Y-axis, and Z-1 and Z-2 axis. (Per this example), the rank and file of this battalion of atoms have 2 Hydrogens facing to the West, with the Oxygen next in line (H/H - O). The next squad of water, connects the H/H to the first Oxygen, followed by its Oxygen, and further East. The Y-, Z-1, and Z-2 axis strings of water molecules shift so that their Oxygen is next to the Hydrogens, while their Hydrogen/Hydrogen structure is next to the other Oyxgen. One literally makes a 3D matrix of H/H - O - H/H - O .... in all 8 directions. Because the free flowing water molecules have the 2 Hydrogen atoms at 104.5 degrees apart, the connected strings of H/H - O ... connecting with other H/H - O, will continue making a reverse O - H/H of 104.5 degrees. H/H - (104.5) - O ... (104.5) - H/H - (104.5) - O - (104.5) - H/H - (104.5) - O .... The lattice structure of water turning into ice creates triangular lattices of (angle) A = 104.5, (angles) B and C being 37.25 degrees. Only when water turns into snowflakes, only having an X- and Y-axis of construction do you see the infinite varieties of the 6-legged snowflake and its many fractal fuzzy branches. So, whereas, free flowing water molecules whirl and spin around in a bigger volume of water, the transition state of water turning into ice, condenses the water volume, and THEN with total alignment of the molecules, the water expands into rigid ice structures. Contraction, then expansion. So free flowing water seeping into a crack through surface osmosis, sits within the rock, and when freezing occurs, the water continues moving further and further into the smallest of cracks in its condensed volume. With final ice formation, the ice then expands outward with all of its triangular latticing in all directions, cracking open the biggest to the smallest of rock fractures. As the day and rock warms back up, the ice melts, contracts down, and then expands to its free flowing watery state, dripping out of the rock, or further penetrating down into newer rock fractures. Repeat the cycle, and you have continual heating, cooling, freezing, cracking, melting, penetrating, ... and further cycles of weather erosion via water, rain, snow, and ice - alongside solar heating and cooling cycles. A little complicated, but it is the arrangement of the Hydrogen atoms to the Oxygen atom that creates the frozen latticing of immense molecular strength that cracks rocks of (seemingly) higher density along their Bravais lattice lines and any crystallization in the rock structures.
@@beeble2003 RUSM. When I said the H2O water molecules align with their 104.5 degrees, these line up and THEY (as ice crystal formations) are what lead to expansion. Water doesn't expand, ice crystals do.
Great topic. A challenge ... Is it even possible to work out an erosion chart of the various mafics, intermediates, and felsics, Which erode faster than the others in their column, but also the side-to-side relatives ... and their intermediate Andesite, Dacite, Diorite relatives. This also considers whether they are phaneritic (visible crystallization) or aphanitic (no visible or micro-crystallization). Mafic (low silicon crystallization) Intermediate mafic-felsic Intermediate-intermediates Felsic (high silicon crystallization) Aphanitic (no visible or micro- crystallization) : Porphyritic (large crystals inside smaller crystallization matrix) : Obsidian glass (aphanitic) Rhyolite (aphanitic) Basalt (aphanitic) Andesite (aphanitic or porphyritic) Dacite (aphanitic or porphyritic) Rhyodacite (aphanitic or porphyritic) Phaneritic (visible crystallization) : Gabbro (phaneritic) Diorite (phaneritic) Granodiorite (phaneritic) Granite (phaneritic) If you expect a top-down or bottom-up columnar erosion of these igneous rock types - such is not the case ! You would expect that large crystalized rocks would fracture and erode into small crystals (quartz and quartzite silicate sand) far faster than micro-crystallizations. Yet rhyolite, with it micro-crystallization, reaching a melted glassy texture, is said to erode faster than its larger crystal granite relative. Mafics with their higher iron content, have higher oxidation rates (rusting), and erode faster than their mafic-felsic and felsic higher silicate content relatives. Horizontal row erosion : Gabbro erodes faster (due to its higher mafic iron content, rusting oxidation) than Diorite, that erodes faster than Granodiorite and Granite with their higher felsic (non-rusting) silicate content. Mafic Basalt erodes faster than intermediate Andesite, that erodes faster than Dacite, that erodes faster than Rhyodacite, that erodes faster than Rhyolite. Intermediate mafic-felsic Andesite, Dacite erodes faster than glassy-iron obsidian, that erodes faster than intermediate rhyodacite, that erodes faster than glassy-quartz rhyolite. Columnar erosion : Large crystallized iron Gabbro erodes faster than micro-crystallized iron basalt, that erodes faster than glassy iron obsidian. Intermediate micro-crystallized or porphyritic Andesite, Dacite, and Rhyodacite erode faster than larger crystallized Diorite and Granodiorite. Felsic glassy-quartz Rhyolite erodes faster than larger crystallized quartz Granite. AS SUCH, ... the erosion factors have mafics with high iron content eroding faster than their right side higher silicate content intermediates and felsics. Larger mafic iron crystal Gabbro oxides faster (erodes faster), than micro-crystallized iron Basalt, than glassy-iron obsidian. The smaller crystal intermediate mafic-felsic Andesite, Dacite, Rhyodacite erode faster than larger silicate crystal Diorite and Granodiorite. Glassy-quartz rhyolite erodes faster than its larger quartz crystallized Granite relative. This makes Gabbro the most-erosional igneous rock, then basalt, to the intermediates of Andesite, Dacite, then Rhyodacite, Diorite, and Granodiorite, ...and finally the most-resistant is Granite with its large quartz crystallization, surpassing glassy obsidian and glassy rhyolite. THUS, felsic quartz sands from Diorite, Granodiorite, and Granite are more-ancient erosions, ... than more-easily rusted and more-recently eroded "black iron sands" from mafic rocks. THUS !, eroded quartz sands from diorite, granodiorite, and granite in the most-ancient past created the oceanic (or land-eroded) quartz sands, that then were sedimentary, becoming metamorphosed into sandstones, ... and if other avenues of subduction, recompression pressures and temperature would change the sandstone back into quartzite and quartz crystals, leading up to granite again.
It is a very cool cycle, isn't it! Interesting that the amount of silica in a rock is a better predictor of weathering speed than grain size -- to the extent that there is (appears to be) an inverse relationship between the silica content and weathering speed. That fits with what Prof. Willsey was saying about quartz being so difficult to breakdown. I also find it interesting that in the set of 10 igneous rocks used in this example that the two extremes (fastest and slowest to weather and/or erode) are both phaneritic.
@@elizabethcross8554 Yup - my corrected research and observation as well ! I need to send this off to my gold hunter, and then he will be able to understand what he is looking at with Great Lakes sand and blacks sands holding the tiniest of gold particles, ... while looking at other mountain slope creeks and streams, ... or lowland deltas, estuaries, swamplands, wetlands, the entire sedimentation rate of these sands, silts, and clays ... tells you so much more of the ancient lay of the land, and where ... you are too far downstream in clays and silts, ... or too far upstream, only bedrock and barely any quartz sands, ... or finding a sweet spot of sand, black sands, and gold, how far to dig down until you reach any bedrock or most-ancient of eroded clays and silts.
@@elizabethcross8554 What becomes even more apparent is looking at these mafic, intermediate, and felsic rocks - with micro-crystallization or large crystallization ... the already known apparent erosion patterns versus the other igneous rocks, ... but then consider if anything of this having to do with the Mohs scale of hardness. Bring out the table again ! Mafic (low silicon crystallization) Intermediate mafic-felsic Intermediate-intermediates Felsic (high silicon crystallization) Aphanitic (no visible or micro- crystallization) : Porphyritic (large crystals inside smaller crystallization matrix) : Obsidian glass (aphanitic) Mohs 5-6 Rhyolite (aphanitic) Mohs 6 Basalt (aphanitic) Mohs 6-7 Andesite (aphanitic or porphyritic) 7 and 6 Dacite (aphanitic or porphyritic) 7? and 6? Rhyodacite (aphanitic or porphyritic) 6 and 6-7 Phaneritic (visible crystallization) : Gabbro (phaneritic) Mohs 6-7 Diorite (phaneritic) 7 Granodiorite (phaneritic) 6 Granite (phaneritic) 6-7 What appears is that Aphanitic micro-crystallization in the Mohs 5-6 and 6 range should erode faster than the higher crystallizations of basalt (6-7), Andesite (6 and 7), Dacite (7? and 6?) and Rhyodacite (6 and 6-7). The mafic-felsic hybrid intermediates appear stronger than their pure mafic and pure felsic counterparts. The phaneritic crystallized rocks appear to hold the higher Mohs scale and range across the 6-7 range. So, Gabbro with larger crystallization and higher mafic iron cement between the crystals oxidizes/rusts out and dissolves fast. All of the other mafics with greater micro-crystallization and lesser amounts of iron cement between the crystals, rust and dissolve out at lesser rates of erosion. This is the opposite of the Rhyolite micro-crystalized felsic silicate crystals with Mohs 6, eroding faster than compared to Granite with larger crystals and Mohs 6-7. Again, the intermediate hybrid mafic-felsics has an iron and silicate structure that predisposes the iron dissolving out, while the silicates remain intact. Yet, these intermediate hybrids, with their lesser iron content obviously appear stronger than their higher eroding iron mafic basalt to the left. Intermediate hybrids with lesser silicate content appear weaker than the higher quartz felsic rhyodacite to the right, with the near-same Mohs 6-7 hardness. But, granite, with the greater volume of larger quartz silicate crystals, and non-existent iron content, erodes more slowly than the hybrid intermediates, the micro-crystallizations, and the mafics. So micro-crystallization versus porphyritic or larger crystallizations appears to be a weakness. More oxidizing iron content in mafics appears as the erosional weakness versus more-resistant quartz silicates in felsics. The Mohs scale does provide a micro-hint of erosional weakness or resistant-hardness tendencies, but for the most part this is an indirect coincidence versus a direct causal property in these igneous rocks. So vastly interesting.
Another very educational episode, thank you Shawn! I thought weathering was a type of erosion, not a different process... I guess I hadn't thought it through properly! So, rocks/minerals alteration in situ v. rocks/minerals transport by water, ice, wind, gravity: I get it :) Translated into French, 'weathering' is 'météorisation', which is a funny word ;)
Water expands when it freezes because, as the temperature drops, the molecules slow down and the forces between them change. Specifically, the hydrogen bonds and repulsive forces between the molecules cause them to settle into a crystalline structure where these forces are balanced. In this structure, the molecules are pushed apart into a hexagonal arrangement, which takes up more space than the liquid form. The repulsion between the atoms in this crystalline structure forces the molecules to adopt a "wider" arrangement, unlike in liquid water where the molecules can move freely and pack more closely together. In short, while water molecules are able to move and adapt to their environment they can slip around each other like sliding around a object in a tight space but as things slow/cool down the electrons need to repel each other perfectly which just happens to form a unique crystalline structure (ice) which just happens to be wider (no squeezing past that object anymore because cannot turn around to do so). So now we are wider and therefore our environment must expand to accommodate our over indulgence. hope that makes sense! edit: I just thought of a great analogy. Imagine yourself going through those rotating doors that only allow one person at a time. While they are moving you can go through (water in liquid form) and when things slow down to a stop (frozen ice) you cannot move through anymore. This is because the molecules are spinning when there is movement so you can get around them when they are not repelling you (facing you) but when things come to a stand still (frozen) there is a repulsion in every direction to balance out the ice so nothing can move everyone is trapped in the mud until things heat up again and people can start sliding by each other. ah still not the best but maybe you get it. Probably best done with animation. Kind of like a chess game, while the pieces can move (always slipping around the repulsion forces) the water is liquid but when there is a check mate nothing can move. Any movement on a check mate would be moving toward a repulsion force (against the rules). Anyway, ice structure is a hexagon to balance out the forces within the molecules and liquid water structure means the h2O molecules can freely move around each other getting in really close compared to the hexagon structure (jamming more stuff into the suitcase = denser)
diametral stress is high, however circumferential is equal to diametral times Pi , according to my old machinery's handbook, strength of materials section. Why a frozen pipe bursts longitudinally.
Ha!, should have put Portland, Oregon in for the frost wedging question. I lose several ceramic flowerpots every year if I leave them out for the winter.
I am 82 years old and that Iron arch to me got they're by being next to an ocean at one time. Think could a Rhyolite volcano could have been too acidy that is why there is a lot of sand If it is you can not say the earth is as old as geologist say it is
The entire Western Inner Seaway, east of the Rocky Mountains (once volcanic island arc), laid down eroded sedimentary rocks, of which these iron-rich sediments, with constant water leaching, turned into these iron-rich layers and beddings. As the Rockies were further uplifted, and the Western Inner Seaway drained out into the Gulf of Mexico, massive miles of geology were uplifted above the surface level. Massive erosion of these sedimentary and metamorphosed rocks then started oxidizing and rusting all these iron-rich sandstone. Vertical and horizontal weaknesses created greater erosion patterns on these uplifts. Pillars, arches, hoodooes, etc. all remain standing, while softer and weaker geologies eroded away. What you see of these ancient sandstones is very ancient metamorphosed seabed sediments pushed miles up .. and now continue eroding away again into their primary quartz and quartzite sand particles, while the iron rust will oxidize down into such red iron sands that eventually decomposed into the very iron atoms, and blow like dust across the land, disappearing from the location to deposit in some other depression or crack (!).
@@jeffbybee5207 If I did go, knowing what I know of the ancientness of the whole geology of that region, I could sit there all day looking and contemplating in 1 direction of the backstory, then turn in another direction and have a further chapter(s) in the backstory, ... until I was fully 360 spun and looked about, and have a massive knowledge of the whole area.
I can't understand your comment, but the Earth is absolutely as old as geologists say. There are multiple different lines of reasoning that all point to the same age.
@@beeble2003 Not sure what you have difficulty about. Laramidia was a W to E aligned volcanic arc island, that got spun clockwise with the Farallon plate subducting under it. It now faces N to S. The American trench is a known sedimentary and metamorphic geology, that took 251+ MYA to sediment up. The up thrust of this trench pushing the entire ancient trench miles skywards, then eroding gives us all of these features. Go to some of the latest YT Myron Cook geology vids of Utah and Wyoming and he shows some of this ... which lead to an email to him (and his astonishment at my understanding of this whole process in greater complexity - being a lay geologist). The Western Inner Seaway sedimented 1/4 inch per 1,000 years. The known geological strata still have 3,000 feet of sedimentary and metamorphosed rock in Utah and the eastern Rockies slopes. The Seaway was 2,000 - 3,000 feet in depth with 1+ mile of seabed accumulating in the period of 250 MYA. The calculations show that the once massive and deep American trench was between Laramidia and Appalachia subcontinents. Part of this discovery deals with YT Dutch Sinse and his earthquake statements showing the North American craton, and his western edge of the craton is this exact remains of the American trench weakened geology.
