Friday night observing - January 29

Short notice but if you read this before Friday night (January 29), go outside and look at the Moon.

Tonight's full Moon is at perigee - the point in its elliptical orbit closest to the Earth so it looks a bit larger than it does normally.

If you go outside around 8:00 pm, you'll see the full Moon in the eastern sky and, just to the left, a bright reddish "star" that's actually the planet Mars.

Go to Sky & Telescope for more information.

Yellowstone Update

On January 18, I posted about the ongoing swarm of earthquakes at Yellowstone National Park.  It's still ongoing and, over the last two weeks, there have been over 1,500 small earthquakes at essentially one location in Yellowstone!  Here's a real-time updated list from the United States Geological Survey (USGS).  Here's a map of Yellowstone, located in northwestern Wyoming, showing where the earthquakes are occurring.

The red line outlines the caldera - the large crater left by the last Yellowstone eruption some 640,000 years ago (there were other earlier ones as well).  Note the earthquakes are all occurring on the edge of the caldera.  While sesimologists are keeping a close eye on things, there's no reason to be worried at this time that these earthquakes are precursors to another eruption.

Earthquake swarms do occur at Yellowstone.  Last year, in December 2008 to January 2009, there were 900 earthquakes and back in 1985 there were 3,000 in a particularly large swarm.   All of these current eartthquakes appear to be located about 10-11 km in depth and aren't shallowing with time (as you might expect if they were caused by magma movement - something we don't want to see).

Anyway, seismologists at the USGS still believe these earthquakes are tectonic and not magmatic.  They're just stress readjustments along faults on the edge of caldera and no big deal.  Hopefully they're correct.

More incorrect TV science

Watched a few minutes of Naked Science on National Geographic Channel tonight.  The show was titled Ice Age Meltdown.  They really should pay a geologist a couple of bucks to help edit these shows - there were a couple of inaccurate statements.

First some background.  Most everyone knows that the outer layer of the Earth is called the crust and it lies over the mantle.  Most people are also aware of plate tectonics, the fact that the outer layer of the Earth is split into rigid plates which move relative to each other over time.

Here's where some misunderstandings occur.  Many people knowing this much assume that the tectonic plates are composed of the Earth's crust.  It's actually a bit more complicated.  Below is a nice image I stole from a geologist's website via a Google image search.

There are two basic types of crust.  Oceanic crust, which is 5-7 km thick, is basaltic (essentially solidified lava).  Continental crust, however, is much thicker (averaging 35 km but thicker under mountains) and granitic in composition (mostly metamorphosed).  Below the crust is a layer of the mantle called the rigid upper mantle.  It's solid rock like the crust although it does have a different composition - it's called peridotite and is mostly composed of the mineral olivine.  Anyway, the crust plus the rigid upper mantle (which extends down to about 100 km below the surface) is called the lithosphere (from the Greek word lithos which means "stone").  The tectonic plates are made of the lithosphere.  Below the lithosphere is a softer layer of the mantle called the asthenosphere (asthenes is Greek for "weak").  The asthenosphere is not liquid, it's a soft solid that flows - think of Silly Putty.

Now how does this relate to a show called Ice Age Meltdown?   Well, during the last ice age (the Earth has had a number of "ice ages" in its history so you shouldn't say "during THE ice age), glaciers extended southward to their most recent maximum extent around 18-20 thousand years ago.  Thousands of feet of glacial ice is heavy.  Here is the mid-Hudson Valley of NY, it may have been a mile thick.  That depresses the crust - actually it depresses the entire lithospheric plate causing it to "float" lower in the mantle ("float" is in quotes because the mantle is not liquid).  This process by which the lithosphere is depressed when there's more weight on it and rises up when the weight is removed is termed isostasy.  It's one reason for local sea level change when glaciers grow and retreat.

So, on this "science" show, on the National Geographic Channel which should know better, they were discussing the crust and mantle of the Earth in relation to isostasy.  The crust rises and falls as it floats on the mantle.  OK, a bit of a simplification.  But then they mentioned, several times, how the mantle was magma and molten.  It's not liquid magma.  You can partially melt it to form magma under some conditions, like by lowering the pressure by thinning the lithosphere, but it's solid (you would never call Silly Putty liquid, would you?).

Is it too much to expect freshman geology accuracy from a supposed science show?  Students in my introductory geology class know better.

College Advising

Great quote on advising from Rate Your Students (a place for anonymous college faculty to bitch).

Advising is a key part of this mission. Our advisors take great care in helping students transition from the loving environment of high school into a world where nobody gives a shit about them. Although we can’t discuss the details of our patent pending advising methods (at least not until the 5th shot), it all comes down to giving each student an identification number and a course catalog. If the morons can’t figure out that they take Biology I before Biology II, then we can assume they won’t master the ATP-ADP cycle either.

Given the increasing hand-holding and mothering we're expected to give our adult students as advisors at my institution (with the bottom line of increasing retention and income), I had to laugh at the last sentence.