Geoawesomeness got my attention today by featuring a You Tube video done by Vox folks a few months ago. The Vox video points out that basically all world maps are wrong in how projections of land masses are variously shown. Aleks Buczkowski from Geoawesomeness gave a lead-in to the Vox video in his posting on it by saying:
Projecting a round surface of the Earth on a flat surface is not an easy task. Scientists are trying to find an optimal way to do it for centuries. In fact the most common map projection that we use almost everyday in Google Maps and other mapping services, has been introduced in 1569 by Gerardus Mercator.
The video from Vox does help to explain the intricacies of map projections and is really worth watching:
Some winter days in Yellowstone National Park are so amazing with clear blue skies and sparkling snow that they just take your breathe away. Luckily enough, I just experienced several of these kinds of days which I packed full of cross country skiing, snowshoeing, and animal watching.
One of the groomed trails that held a good snow base until about early afternoon is the Blacktail Plateau Loop. The trail follows melt-water channels that are associated with “Retreat Lake”, which was formed by the Beartooth glacial ice mass blocking the lower end of the Grand Canyon of the Yellowstone during the Pleistocene.
The Tower ski trail provides access to the Grand Canyon of the Yellowstone area. A favorite stop of mine is the Calcite Springs overlook where the thermal springs lie south of the overlook, on the west side of the Yellowstone River and Pliocene/Pleistocene sediment and basalt are on the Yellowstone River’s east side.
A groomed ski trail also accesses the Upper Terraces of Mammoth Hot Springs. However, after a few days of spring-like temperatures, the snow was so melted back that I just used my snowshoes to trek through the icy slush. Some thermal features were still covered by snow and slush, but others appeared much more vibrant against the white snow/slush blanket.
Aphrodite Terraces lie a short way north of the White Elephant Back Springs:
My favorite thermal feature of the Upper Terraces is Orange Spring Mound. The spring is supported by a fissure ridge and is intermittently active. Because of its low water discharge and subsequent slow growth, it has built up a characteristic cone shape.
All in all, it was perfect wintertime fun trekking around in Yellowstone. Can’t wait to get back there when the bears come back out from hibernation!
Much of my research has been focused on Cenozoic sequence stratigraphy of continental basin-fill in southwestern Montana. This approach to the stratigraphy of continental deposits has facilitated correlation of stratigraphic units both within and among the various basins of this area. I recently gave a talk about my work in this area at Montana Tech of the University of Montana. Here’s the You Tube version of my talk:
NOAA’s SOS data center has a new earthquake data set animation for events that occurred from 2001 through 2015. The Science on a Sphere’s animation shown above is described on their web site as:
This animation shows every recorded earthquake in sequence as they occurred from January 1, 2001, through December 31, 2015, at a rate of 30 days per second. The earthquake hypocenters first appear as flashes then remain as colored circles before shrinking with time so as not to obscure subsequent earthquakes. The size of the circle represents the earthquake magnitude while the color represents its depth within the earth. At the end of the animation it will first show all quakes in this 15-year period. Next, it will show only those earthquakes greater than magnitude 6.5, the smallest earthquake size known to make a tsunami. Finally it will only show those earthquakes with magnitudes of magnitude 8.0 or larger, the “great” earthquakes most likely to pose a tsunami threat when they occur under the ocean or near a coastline and when they are shallow within the earth (less than 100 km or 60 mi. deep).
I came across a good posting on Carbon Brief that gives a succinct historical background for designating the new geological epoch, the Anthropocene, and thought I’d pass it on. As defined by the English Oxford Living Dictionaries, the Anthropocene is:
Relating to or denoting the current geological age, viewed as the period during which human activity has been the dominant influence on climate and the environment.
The Anthropocene is not a formal geologic time unit yet within the geologic time scale – that label will take awhile. But the Working Group on the Anthropocene (a part of the Subcommission on Quaternary Stratigraphy) gave their recommendation to formalize this time unit to the 35th International Geological Congress in Cape Town, South Africa on August 29, 2016, so there is some progress. The working group suggested that there are options for marking the beginning of the epoch, such as c. 1800 CE, around the beginning of the Industrial Revolution in Europe or about 1950, where the boundary
…was likely to be defined by the radioactive elements dispersed across the planet by nuclear bomb tests, although an array of other signals, including plastic pollution, soot from power stations, concrete, and even the bones left by the global proliferation of the domestic chicken were now under consideration. From The Guardian, 8/29/2016.
Anyways, it’s worth reading the posting on Carbon Brief by Sophie Yeo about the Anthropocene, and I’ve included one of the posting’s infographics below to peak a reader’s interest.
The Laramie Mountains are part of the central Rocky Mountains in southeastern Wyoming. Archean and Proterozoic rocks form the bulk of the mountain range due to late Cretaceous–early Eocene (Laramide) basement-involved uplift. Hogbacks made of Paleozoic to Mesozoic age rocks flank much of the
Precambrian cored mountain areas. But what sets the Laramie Mountains apart from the adjoining Colorado Front Range and even the western Great Plains is that upper Eocene to Miocene strata are preserved within the Laramie Mountains and on its sides as paleovalley fill. The reasons for this unusual paleovalley fill preservation can probably be tied to the Laramie Mountains being much lower in elevation than the adjoining Colorado Front Range and that they were not glaciated during the Pleistocene.
I went on a field trip a few days ago specifically to look at the Laramie Mountains Tertiary paleovalleys. It was a really good trip. Emmett Evanoff led the trip and because he’s spent so much time working in the area, he had much info and insight on the paleovalleys. What follows are a few photos from the trip:
My field season is in full swing. I recently spent time with students from the Webb Schools in Claremont, CA, during their annual sojourn to southwestern Montana. We prospected a few Tertiary localities, with the students making some good fossil mammal and fossil invertebrate finds. We were also extremely lucky to have a southwest Montana landowner give us a tour of a buffalo jump that is on his land. The following photos are from our various fossil site and buffalo jump field adventures.
Volcanic stratigraphy is hard to ignore when touring through the Teton to Yellowstone National Parks (YNP) area. Three major volcanic eruption cycles occurred during the last 2.1 million years and resulted in hundreds of feet of volcanic rock. The eruption cycles make a good basis for separating the volcanic rock units and consequently there are three major volcanic stratigraphic units. These major units consist of ash-flow tuffs that erupted at the peak of each cycle and include the Huckleberry Ridge Tuff with an age of 2.1 million years, the Mesa Falls Tuff with an age of 1.3 million years, and the Lava Creek Tuff with an age of 0.64 million years.
The type sections of the Huckleberry Ridge Tuff and the Mesa Falls Tuff are fairly accessible. The Huckleberry Ridge Tuff type section sits at the head of a large landslide about 1.5 miles south of the YNP’s south gate and 1 mile northeast of the Snake River Bridge. It’s a big landslide, so it’s easy to spot from the highway. The type section mainly contains welded rhyolitic ash-flow tuff. This huge eruptive event (one of the five largest individual volcanic eruptions worldwide) associated with the Huckleberry Ridge Tuff formed a caldera more than 60 miles across.
The Mesa Falls Tuff type section is really accessible as it is alongside Highway 20, about 3 miles north of Ashton, Idaho. The type section consists of airfall tuff, partially welded tuff that has an agglomeratic base. The eruption associated with the Mesa Falls Tuff formed the Henrys Fork Caldera which is in the Island Park area west of YNP.
The Lava Creek Tuff type section is much more difficult to access as its type section in the upper canyon of Lava Creek, about 8 miles into the backcountry of YNP. There are a couple reference sections that are easier to reach, and one is in Sheepeater’s Canyon, about 0.5 miles northeast of Osprey Falls. The Lava Creek Tuff is also readily seen in the south-facing cliffs along much of the Gibbon River. The eruption associated with the Lava Creek Tuff created the Yellowstone Caldera, the 35-mile-wide, 50-mile-long volcanic depression that dominates the present YNP landscape.
There are many more volcanic units associated with the three major eruptive cycles. But spending time looking at the major ash-flow tuff units is a good way to begin to delve into Yellowstone geology.
My first trek into the Carolina Sandhills began with a visit a couple days ago to Weymouth Woods Sandhills Nature Preserve in Southern Pines, North Carolina. Weymouth Woods is a great place not only to hike through part of the Sandhills, but to also see the longleaf pine forest that readily grows on the sands. The land for the preserve was donated to the North Carolina Division of Parks and Recreation in 1963 by Mrs. James Boyd. Her father bought the land in 1903 so that a part of the region’s original longleaf pine forest would survive. In fact, there are old-growth 400 to 500 year-old longleaf pines still flourishing near the Weymouth Center.
Back to Sandhills geology – the Sandhills are a Quaternary aeolian blanket of sands and dunes that cover part of the Coastal Plain of the Carolinas. That the sands exist in the Coastal Plains uplands of the Carolinas has been known for some time, but recently Moore and Brooks used LIDAR data to show an extensive Upper and Middle Coastal Plain upland aeolian landscape. Moore and Brooks describe their findings as:
“Although primarily an Upper Coastal Plain/Sandhills phenomena, these large-scale eolian features are also present in parts of the dissected uplands in the Middle Coastal Plain immediately east of the Orangeburg Scarp in South Carolina and in the Middle Coastal Plain portions of North Carolina. While the timing is likely related to riverine source-bordering eolian dunes, the sand source for many of these upland eolian deposits appears to be derived from upland incisement and erosion by primarily 1st order streams. In fact, many sources appear to originate from the incised borders of broad dissected coastal uplands with numerous small feeder streams and streamhead sources. In other words, the downcutting and incisement events appear correlated with dune and eolian sand-sheet formation in the uplands where extensive erosion would have provided a plentiful sand source for remobilization as eolian dunes. Although the timing of upland incisement is not clear, it likely occurred most recently during or sometime just after the last glacial maximum when large river systems in the Southeast were transitioning from braided to meandering and incised fluvial systems.”
This is defintely different geology from the Montana Cenozoic continental basins than I’m used to. So it was a great change and fun geology to think about. And – if a hike through Sandhills country is on your list, a visit to Weymouth Woods is in order. I used the trails at both the main Weymouth Woods acreage that are by the visitor’s center and also hiked the Paint Hill trails that are also on State Park lands. The Paint Hill trails are a part of the Weymouth Woods Sandhills Nature Preserve, but are located about a mile southwest of the main woods. Both areas are amazing!
Much has been written about Machu Picchu since its rediscovery in 1911 by Hiram Bingham and his expedition crew. And although I was truly amazed at the ruins of Machu Picchu when I hiked around it a few months ago, I was mesmerized by the area geology as soon as I got off the train at Aguas Calientes – the town at the base of Machu Picchu. Consequently, it’s the geology of Machu Picchu that I’ll talk about in this blog rather than the ruins. But – for those who would still like to read more background information on Machu Picchu, the Library of Congress has a good online bibliography site for a starting point- Machu Picchu: A Brief Bibliography.
The geographic setting of Machu Picchu –
Machu Picchu lies in the south-central Cordillera of the Peruvian Andes, known as the Cordillera de Vilcambamba. Cusco, the nearest major city, lies about 50 miles southeast of Machu Picchu. Most sojourners like myself access Machu Picchu via the Sacred Valley either by train or by walking the Inca Trail, and stay in Aguas Calientes during their time exploring Machu Picchu.
The geologic setting of Machu Picchu –
As soon as I got off the train at Aguas Calientes, I could see that it was a granitic dominated geology. Large remnant exfoliation sheets, typical features of granitic landscapes, cling to the mountainsides in every direction that I looked. Canitu and others (2009, p.250) describe the geology of the the Machu Picchu site as:
“The bedrock of the Inca citadel of Machu Picchu is mainly composed by granite and subordinately granodiorite. This is mainly located in the lower part of the slopes (magmatic layering at the top). Locally, dikes of serpentine and peridotite are outcropping in two main levels; the former is located along the Inca trail, near Cerro Machu Picchu (vertically dipping), the latter is located along the path toward ‘‘Templo de la Luna’’ in Huayna Picchu relief.”
The granitoid pluton of Machu Picchu is part of the larger “Quillabamba granite”, which is a magmatic complex now exposed in the eastern Cordillera of central Peru. The Machu Picchu pluton, along with numerous other areal plutons of this magmatic complex, were intruded into an axial zone of a Permo-early Jurassic rift system. Isotopic age data that more tightly constrain this magmatic activity include a (U–Pb) age of 257 +3 My for the Quillabamba granite and a biotite Rb-Sr age of 246 + 10 My for the Machu Picchu pluton (from Lancelot and others, 1978: U/Pb radiochronology of two granitic plutons from the eastern Cordillera (Peru) — Extent of Permian magmatic activity and consequences. Int. Journal of Earth Sciences, 67(1), 236–243). The current exposure of the Machu Picchu pluton at such a high elevation is due to a tectonic inversion of the rift system’s axial zone. The inversion is a result of Andean convergent deformation that occurred largely during the Eocene (Sempere and others (2002) cited in: Mazzoli and others, 2009).
The site-specific geologic structural setting of Machu Picchu is that the citadel ruins lie within a northeast-trending graben. The graben is delineated by two normal faults with the upthrown side on the northwest including Huayna Picchu and the upthrown side on the southeast being the block that contains Machu Picchu Cerro. As an aside, there are great 1-3 hour hikes that can be done, both to Huayna Picchu and to Machu Picchu Cerro. I did the hike to
Huayna Picchu with a great group of people, so it was a fun hike made even better by spectacular views from the top of Huayna Picchu.
Building stone of Machu Picchu –
Lastly, because the ashlar method of stone block construction (a method where stone blocks are dry fit together so well that it is impossible to slide a piece of paper between the blocks) used in Inca architecture is so fascinating, I’ll include a few words about the stone used in this method at Machu Picchu.
The building stone of the Machu Picchu citadel ruins was quarried from the area granitoid rocks. Canuti and others (2009, p. 256) in their study of Machu Picchu slope instability note that:
“As historical consideration, the data collected suggest the possibility that the site of Machu Picchu could have been selected by Incas also because of the availability of two large block deposits, useful for constructions: one on the so called ‘‘cantera’’ and the second in the paleo-landslide recently discovered.”
The “cantera” mentioned above is the quarry that was used during the original construction of Machu Picchu. It is located between the Sacred Plaza and the Temple of the Sun at Machu Picchu. It looks like just a chaotic pile of rocks, so is probably not a point of interest for most visitors. The paleo-landslide also mentioned above as a potential source for granitic building material is an area located on the northeast flank of the Machu Picchu citadel ruins. Canuti and others (2009) suggest that it is probably some tens of meters thick and luckily their deformation monitoring did not detect mass movement.
And so ends my 5-part blog series on my adventures in Peru. All I can say is – go there if you get a chance. It is an amazing place!