Archive for May, 2019

Constructive & Destructive Landforms at Mount Rainier National Park

May 30th, 2019

One common frame used to introduce landforms in introductory Geology courses is the idea of constructive and destructive forces that create and change them. (See, for example some K-12 resources here and here.) Constructive processes like the the deposition of sediment and extrusion of lava build landforms by adding material at the surface. Destructive processes like weathering and erosion and explosive volcanism shape the surface by removing material.

If you go to the Paradise Visitor Center in Mount Rainier National Park, you can observe this dichotomy at work just by comparing the north and south. Looking to the north is the park’s namesake: Mount Rainier. The smooth, rounded shape of this composite stratovolcano is primarily the result of layered ash, rubble, and lava over the past 500,000 to a million years, piling up over 14,000 ft high (NPS). There are glaciers eroding the flanks of Mount Rainier, but the recent volcanism of the past few thousand years means the overall shape is more reflective of volcanism than glaciation.

View to the North: Mount Rainier

Contrast this with the view to the south. Rather than a single smooth and rounded profile, the Tatoosh Range is characterized by several jagged peaks with names like “The Castle” and “Pinnacle Peak”. This mountain range is the result of extensive weathering of an ancient pluton, which was originally emplaced in the Miocene (14 million years ago; USGS 1963; Mattinson 1977). The Tatoosh pluton was exposed at the surface and actively eroded by Pleistocene glaciers long before Mount Rainier existed.  With millions of years of erosion at work, destructive forces are more obvious in the Tatoosh Range than on Mount Rainier. It displays classic glacial features like the horn of Pinnacle Peak, the col between Plummer Peak and Denman Peak, and the converging U-shaped troughs below Plummer Peak.

View to the South: Tatoosh Range (Paradise Visitor Center in foreground).

Lots of Rain v. Many Rainy Days

May 16th, 2019

The other day while on the phone with my sister, she complained about how bad the weather was. “It’s rained like every day since April 1st” was the statement. That was an exaggeration, so she then modified that statement to say it’s been really wet this spring, and she’s had few opportunities to let the boys play outside in the sun. So then I wondered… is she right? Or is she just participating in a favorite past time of complaining about the weather? She lives north of Boston, so I decided to take a look at the data from a long-running station at Lowell, Massachusetts.

Distribution of total precipitation between April 1 and May 10 in Lowell, Massachusetts

It’s true that 2019 has had a wet spring. Of the 127 years of data at Lowell, 9 years had enough missing data I had to toss them.  That leaves 118 years.  Of those, 2019 has seen the 12th most precipitation between April 1 and May 10 (7.73 inches; the 91st percentile). However, my sister has only lived near Lowell for about 15 years, and in those 15 years, 2019 ranks 5th… so above average, but nothing special.  In fact, neither of her sons has experienced fewer than 6 inches of rain from April 1 through May 10… all they know is wet springs!

Before I called her back to tell her she’s exaggerating, I decided to dig a little deeper.  You see, my sister didn’t actually say there’s been a lot of rain; she said there had been many rainy days. That’s different. If we track the percentage of days on which rain (sometimes with snow) fell in Lowell since April 1, we find that my sister is on to something.  It has rained 25 days — about 62% of the days since April 1 — and that is a record.  Yup, in 118 years Lowell has never had so many rainy days between April 1 and May 10.  My sister’s smart, but I didn’t expect she’d be that good.

Distribution of the days between April 1 and May 10 with precipitation greater than 0.01 inches in Lowell, Massachusetts

Anyway, the lesson here is that my sister, like many people, would rather have a lot of rain on a few days than a little rain on many days. It’s not the rain so much as lack of sun that gets to people. This is partly why a city like Seattle (36 inches/year) is famous for being rainy even though cities like Cleveland (39 inches/year), Boston (44 inches/year), and New York City (50 inches/year) all receive more precipitation.  It’s not that Seattle gets a lot of rain; it’s that it’s often raining. Seattle has 152 days with precipitation a year, but Boston only has 126, and New York has only 122. Think about that — NYC gets 38% more precipitation but 30 extra days without any precipitation!

Total annual precipitation and number of days with greater than 0.01 inches water equivalent of precipitation in four US cities

Cleveland, for the record, has 154 days with precipitation a year on average thanks to it frequent lake effect snow. All data are from NOAA’s Climate Data Online.

New paper on crinoids of the Kalana Lagerstätte (Early Silurian) of central Estonia

May 14th, 2019

Bill Ausich (The Ohio State University), Oive Tinn (University of Tartu) have a paper that has just appeared:

Ausich, W.I., Wilson, M.A. and Tinn, O. 2019. Kalana Lagerstätte crinoids: Early Silurian (Llandovery) of central Estonia. Journal of Paleontology doi.org/10.1017/jpa.2019.27

It was an absolutely delightful project that was thoroughly documented in this blog. Last summer Bill and I traveled to Tartu, Estonia, to work with Oive on describing the extraordinary crinoids of the Silurian Kalana Lagerstätte. A Lagerstätte is a sedimentary deposit with exceptional fossil preservation. It is a privilege as a paleontologist to work on one. As you can see from the images, the crinoids here are well preserved indeed. I’ll let the paper’s abstract tell the story:

Abstract.—The Kalana Lagerstätte of early Aeronian (Llandovery, Silurian) age in central Estonia preserves a diverse shallow marine biota dominated by non-calcified algae. This soft-tissue flora and decalcified and calcified crinoids are preserved in situ in a lens of microlaminated, dolomitized micrite interbedded in a sequence of dolomitized packstones and wackestones. Although the Lagerstätte is dominated by non-calcified algae, crinoids (together with brachiopods and gastropods) are among the most common organisms that were originally comprised of a carbonate skeleton. Two new crinoids are described from this unit, Kalanacrinus mastikae n. gen. n. sp. (large camerate) and Tartucrinus kalanaensis n. gen. n. sp. (small disparid). Interestingly, these two crinoids display contrasting preservation, with the more common large camerate preserved primarily as a decalcified organic residue, whereas the smaller disparid is preserved primarily in calcite. Preservation was assessed using elemental mapping of C, Ca, S, and Si. Columns have the highest portion of Ca, once living soft tissue is indicated by C, S was dispersed as pyrite or associated with organics, and Si is probably associated with clay minerals in the matrix. This new fauna increases our understanding of the crinoid radiation on Baltica following Late Ordovician extinctions.

The top image and that above shows the new crinoid Kalanacrinus mastikae. Look at those gorgeous arms and the carbon films in the calyx that may represent internal organs. The species is named in recognition of Viirika Mastik, an Estonian graduate student who helped us in innumerable ways, and she was very patient with the sometimes clueless Americans! The genus, of course, is named for the deposit. (Scale bar is 5.0 mm.)

Here is another specimen of Kalanacrinus mastikae. Note the small angular, twiggy fossil below the calyx. I think it may be a green alga similar to the modern Hydrodictyon but marine and with larger cells.

Say hello to the new crinoid Tartucrinus kalanaensis. It’s pretty obvious how we came up with these names. Note again a carbon film in the calyx that may be from internal organs, possibly the anal sac. (Scale bar is 5.0 mm.)

The location and stratigraphy of the Kalana Quarry.

Several slabs of Kalana material. What a joy it was to study them for long, uninterrupted days.

The paleo lab at the University of Tartu, with Bill working in the background.

I loved this brand new Leica photomicroscope (model S9i).

Oive does excellent geochemistry, so she handled the elemental mapping. This example shows a close view of a Kalana crinoid column, with the elements C, Ca, S, and Si mapped. As stated in the abstract, columns have the highest portion of Ca, once living soft tissue is indicated by C, S was dispersed as pyrite or associated with organics, and Si is probably associated with clay minerals in the matrix.

Thank you to our excellent Estonian colleagues!

From the left is Oive Tinn, Mare Isakar, Bill, and Viirika Mastik.