Black Hills Volcanism Evidence - Extrusive

[Music] alright ladies and gentlemen welcome hey I'm driving I'm just coming up unpacked all the reservoir I am getting ready to show you evidence of past volcanic activity in the Black Hills so specifically we're gonna talk about extrusive igneous rock today and see some evidence of that that's all rap I'm here at I'm looking at the lake right now I'm getting ready to turn off so here in a second we're gonna be at the spillway and I will get to show you the first example of some of that volcanic evidence just pull off to the side on this little service road that goes up and on top of the spillway all right so I got down to the end of that road and drove walked out here behind the spillway at back told me they cut this spillway into this hillside when they've made the dam at pack Tola to the lakes right behind me on the other side of that school specifically we're looking at those black rocks right there those bands of black rock kinda going at an angle vertically that black rock is called basalt and a lot of what this spillway was carving to you is basaltic Rock the basalt is just lava flow at some point in the past magma came up out of the ground and flowed across the land you got this basalt here now it's been tipped up on its side because over the thousands and millions of years the Black Hills have been changed and pushed up and twisted and pushed around it doesn't stay flat when after its laid out on the ground but we do have evidence here now the problem with this site even though we can see it it's very hard to get over there and actually get hands-on with it so we're gonna keep moving all right we're coming up and Custer Peak Road here on the left it basically immediately turns into gravel all right so we got a lot better view a Custer peak right here you can see that thing looks like a very big column just sitting out here in the middle of the Northern Hills that's actually volcanic rock so we need to see if we can get up to the top all right so it's winter time they got the road closed two-wheeled vehicles if you had a snow mum someone Beall or snow machine you can get up here at least we can get this close and get a good view of Buster Pete from the side get a good view of the watchtower and the slope going up and specifically the rocks that it is built on that is rhyolite that is a an igneous rock that is extrusive it's a strong grey rock and the early settlers knew that that was a volcanic rock type so they actually mistook Custer peak and several of the other surrounding peaks as extinct volcanoes in fact some of the early reports coming out of the Michael's was that there were volcanoes in the Black Hills well it's because they saw Hills like Custer Pete it's kind of a shame we can't get any closer but this is what we get for now this summertime you can get a lot closer right get up there get a sample of the rhyolite take it check it out I'm gonna definitely come back this summer what I want you to do now before I move on to the next site is it going to that roadside geology book when this video gets over start looking up with dr. Paul grease Lee said about the Custer peak and these other named peaks in the northern Black Hills so I'm gonna move up the road you know that's one of your first tasks all right so I came up highway 385 and I'm on the junction of emo Road and 385 so you basically if I go off in that direction I head back to Nemo and I'm basically a place where old boondocks used to be but even before that it was called Brownsville and it's still called Brownsville it's an old mining town on basically a ghost town they're still just enough people here to have a volunteer fire department which is what's behind me that's not why I'm here I'm here because this road cut on the junction at this northeast corner of this rope Junction this road cut it looks just like a hill full of dirt or the road had to like cut the hillside away but it's a good thing they did because it actually exposes a lot of evidence of volcanic activity in the past you're looking at essentially a huge mixture of volcanic ash of tuff of basically the all the stuff that comes out when I'm tired plastic flow or a pyroclastic explosion happens this stuff is very crumbly actually to walk up on it but get really close and look at it this grayish material that's actually like volcanic ash this stuff right here this stuff that stuff is volcanic ash and silt and mud and everything else mixed in and all these rocks you see my hand they're all these rocks our parts all the overlying rocks that were here on top of this area when the place exploded you can see that there aren't all kinds of stuff here you've got sand stuff you've got siltstones mud stones that were here prior to the explosion here's a good example of a piece of what looks to be like a mud stone that's not part of the explosion that is caught up in it you've got the actual am I trying to get my rocks my mocking route and take a sample of this thing bring it back and show you guys okay so this this whole area like I was saying this whole area is basically the is the start southernmost start of what is volcanic a volcanic pyroclastic event so I'm gonna I'm gonna get to the actual epicenter of it so to speak the crater the vent and see the wing all right so I'm at the tomahawk Country Club which is on 385 on the way to leading Deadwood they were gracious enough to let me have permission to cross the property and during the off-season it is on private property the site I'm going to so you do have to have permission to go check it out this is the guy stuff I do for you guys come out in the middle the hills and hike around in the hill the winter so you can see we're out here in the millimolar all right onward see that black rock right there that there is that's obsidian we are we are on top of the tomahawk diet stream it is to the best of anyone's knowledge it is the only case of a volcano actually or a volcanic event anyway actually erupting on the surface in the Black Hills in geologic history this black rock proves it all might not look like much on first glance it looks just like basalt or some of the darker gabbros but you get up close and i'm gonna take some samples home for you this stuff is volcanic glass it shines like volcanic glass it shatters like volcanic glass it cuts like volcanic glass like the guy that I came up through with found out last summer but it doesn't look like the smooth volcanic glass that you would see on some place like Hawaii we see the nice smooth reflective volcanic obsidians free to make arrowheads out of it or things like that it looks rough it looks like it's been through a lot of stress and around it and inside and scattered in through it is all of this stuff okay this stuff is like white it looks like it's just glued together a bunch of bits and pieces of little stuff okay this stuff is tough and I don't mean like it's tough like it's hard I mean it is tough that's the name of it it's volcanic tuff and what it is it's just a name for when ash is under such great pressure that it carries bits and pieces of everything else around it welds it are cemented together we call this stuff volcanic tuff and this stuff is all over the tama heck Country Club you just go golfing here all along the little trails for the karts all on the tee boxes is this tough stuff and people drive by at all time I see it and I pick it up all right so I made it at the top this is why you don't walk up on this thing and this is actually why I'm not going to post the GPS coordinates for this mint is if you come walking up on this thing from the other side of this hill you walk through this bush that you're looking at on the bottom of the screen you can basically fall 85 feet to your death okay but this is the vent this is the vent where well I'll let you guys figure that out what happened that's why we came out here I'd someone to show it to you I'm standing on more of that obsidian so I don't want to get too close to the edge because it's very crumbly that whole wall of that mint is lined with that obsidian rock so one last look at the volcanic vent here at the tomahawk that dream before I move on to the next and final site and this week but like I said before I'm not posting GPS coordinates to this thing if you want to come out here that's on you right well they can ask you to be very very careful images no this is on private property I did receive permission from the owners of tomahawk nothing love to come across during their offseason and check this out tomahawk diet tree our own little volcano right here in the Black Hills who'da thought of it it's not Mount Rainier it's not Mount st. Helens definitely not as cool as those events were but if you were here when this thing went off you didn't know about it so what I want you to do now I want you to go into the roadside geology book and start researching it I want you to figure out what type of volcanic event this really was how does this fit in with what you already know about volcanic events like those at Mount Rainier or like those are like Mon Aloha in Hawaii where does this fit what is it most similar to how does this fit into the big picture of volcanism we know it's an extrusive igneous event there's obsidian sitting on the ground here in the Northern Hills by a golf course that's extrusive but now it's on you a going to my last site I'm actually heading out out of the Black Hills just hair when I go down into Deadwood go out towards Sturgis and I'm gonna see if I can get out to Bear Butte before the Sun Goes Down is that it's going to be our last stop on this whirlwind tour of extrusive igneous evidence all right here we are our final stop Bear Butte probably the most famous out of all of the stops definitely more famous than Custer peak and packed Cola definitely more famous than the volcano nobody knows about right so this place formed in basically the same way that Custer peak did that crow peak up near Spearfish did that tere peak by leading Deadwood and several other named peaks to include Devils Tower all form the same way and you're gonna look this up again yep you guessed it roadside geology is South Dakota now I hope I've given you a little bit of a insight into the fact that we have a ton of examples of extrusive igneous volcanism and in the Hills historical volcanism it's everywhere you just got to know what to look for guys extra credit if you want to come out to Bear Butte that's the main one that's the big one and it's a great place to come if you want your extra credit drive out here you can drive do it in any car it's all paved roads come to this entry gate where you have to start paying beyond this point if you come to this entry gate you get your extra credit if you take a picture next to this sign like this ah okay just like that can't be anything else got to be like that you don't have to have the beard though it's all right if you've got the money in the time go in check out the visitor center go in go take a hike up that up to the top of that if you've never done it before it's a spectacular view do it on a clear day and like May or June awesome it is beautiful alright there's lots of cultural significance to this place with lots of geologic significance to this place there's a lot of historical significance to this place when the early settlers came here this was a big landmark so I highly encourage you to get out here alright ladies and gentlemen thanks for watching I'll see you next time and you're probably hear me talking here in a minute so later [Music] hey Brandon Brandon Mills guess what I found right there on the side of the road on the way to Deadwood from Sturgis I'll bring my samples back and you can check them out compared to what you have brought me [Music]

Channel: Lance Schroeder

Views: 558

Keywords: Black Hills, 2018, Volcanism, Extrusive

Id: nYDcP7QSxwo

Length: 15min 0sec (900 seconds)

Published: Sun Apr 22 2018