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By Jay, on September 3rd, 2010% To be honest, I was sort of hoping for more of an impact this far inland from Hurricane Earl. Maybe not as bad as Fran or Hugo, but something. The folks that live out on the Outer Banks probably took some damage but they’re used to and can handle quite a bit way out there.
Oh well. The 2010 Atlantic Hurricane Season still has quite a bit of life. I really wanted to get some swollen streams around here to examine something with you. We have this type of regolith, or highly weathered bedrock, that rests right above the actual bedrock surface in the Piedmont of North Carolina. Sometimes referred to as Partially Weathered Rock, or more commonly Saprolite, I wanted to evaluate if this material shows evidence of weathering and erosion, or if it tends to weather in place, in the stream banks anyhow.
I’ll need some water chugging down these streams for that. Unfortunately, the only times this summer we’ve had the types of heavy rainfall required have been very late at night. Fret not. There’s plenty of Hurricane Season left. Hopefully, we get some good rain on a day I can run over to a stream near . . . → Read More: So No Hurricane Earl
By Jay, on August 4th, 2010% I love taking photographs of downtown Raleigh. It’s a beautiful skyline in the warm months, especially right at dusk. Every so often I go lurking the streets for unique angles and views as those often tell more of a story.
Many of the buildings—short, medium, and tall—use bedrock for their foundations and ornamental stone faces. Looking at these rocks in the urban geologic setting is good practice at rock identification. Remember I gave the overview on “weathered” versus “un-weathered’? What’s cool about examining rocks that are building materials is that by virtue of the processes of cutting and polishing, you get a pretty good exposure of the “un-weathered” surfaces of these rocks. Check out Figures 1 and 2. Both are considered granite.
Fig. 1 – Granite at the Base of the NC Museum of Natural Sciences, Raleigh, NC – photo by J. Sents
Fig. 2 – Granite Blocks at the Base of Wachovia Capital Center, Ralegh, NC – photo by J. Sents
Well what’s the deal? If they are both granite, why do they look so different? Well let’s take it from the basics upward. First, there . . . → Read More: Urban Geology
By Jay, on July 3rd, 2010% I got a great couple of questions from my friend Tuesday. She asked,
If dinosaurs are millions of years old, how do we even have their bones? Based on the mathematical equations they give us, those bones would be totally deteriorated, would they not?
A bit more involved, the answer is but painless it will be. The first question is one of fossilization. Dinosaurs were the “rulers” of the Mesozoic Era on the Geologic Time Scale. Mesozoic means middle + life, and is named such because it falls between the time of Ancient Life [Paleozoic], and New Life [Cenozoic]. The fossil record and correlation were all we had before modern dating methods such as radiometric dating became available.
Fossilization of something is more difficult than one would think. A good handful of conditions and processes must occur/not occur in order to fossilize something in the first place, and then prevent it’s destruction over long periods of time. When something like a dinosaur is killed and quickly buried in a substantial thickness of sediment [say from a flash flood], it’s cut off from scavengers, weather, bugs, etc.
So what happens? Well the organic parts will decay quickly. Where these remains are, . . . → Read More: Fossil Questions
By Jay, on June 10th, 2010% My friend and geolojay reader Kathy just asked me this question:
Question for Jay…. I’m watching “How the Earth was Made”. Why are the Himalayas not volcanic? India is subducting under Asia like what is happening under Mt St Helens and “friends” [meaning Cascade Range], right? What’s the difference?
That is a great question. The Himalayas are representative of a modern and active mountain-building event, called an orogeny in geologic parlance. Both the Himalayas and the Cascade Range are the result of plate-to-plate collision in the Theory of Plate Tectonics.
The difference between the Himalayas and the Cascade Range volcanoes is based on density of the lithospheric plates. Yes. The Cascade Range is caused by subduction of more dense ocean crust into and underneath lighter, lower density continental crust. As the oceanic plate dives deeper and deeper, the ocean crust warms, melts, and rises upward through the overriding continental crust “inland” from the plate collision boundary. As that molten rock punches through the continental crust, a curvilinear series of volcanoes, generally parallel to the plate collision boundary, begins to form.
Cascade Range Subduction from J. Wiley & Sons – 2010
In the case of the Cascade . . . → Read More: Himalayas Question
By Jay, on May 24th, 2010% My friend was showing me some photographs the other night as part of a discussion on digital cameras. After sending me this photograph of a school of Jellyfish at the Monterey Bay Aquarium, we started talking geology.
Photograph by M. Schneider – 2010
Jellyfish are an interesting organism to say the least. Those shown in the photograph are the adult phase of the marine animal in the phylum Cnidaria called a medusa. Jellies reproduce asexually which in simple terms means that there males and females that both self-fertilize. I’m not going into nut and bolts of that whole part here. However, when the medusa phase reproduces it releases thousands of eggs into the open waters of the ocean. The eggs that fall to the ocean bottom may eventually become larvae. If the larvae reach a solid, hard substrate, their chances of continued life increase during the polyp phase of the cnidarian.
If the polyps grow and proliferate, they extract carbon, oxygen, and calcium from the ocean water. They reconstitute these elements into calcium carbonate if the ocean water temperatures are warm enough, and begin to build an exoskeleton. The exoskeleton becomes a sort of high rise apartment complex for . . . → Read More: Jellyfish
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