Geology with First Graders

Last week, based on an invite from the teacher, I paid a visit to my oldest daughter's first grade class to talk about geology.  I knew they had been learning about sand, so my job was to take it up to 11.  I also knew, based on what my daughter brings home, that they had previously talked about solids, liquids, & gases, but otherwise they don't get a whole lot of science in first grade.

I brought with me some samples; the ONU Geology program has lots of samples of rocks & sands (obviously), so I took some especially relevant ones to show the kids.

The main point I tried to get across to them is this: different kinds of sand come from different kinds of rocks.  I figured for first graders that wasn't a bad place to start.  The idea is to have them connect in their minds that rocks, when eroded, will form sand, and that there is a direct connection between these two kinds of materials. This is, really, their first introduction to the rock cycle.

I took with me 4 samples of sand.  The first one is a typical quartz sand in a jar that had a couple of nice shells in it.  That one I passed around first and had each student rotate the jar of sand until they found the secret prize inside.  Lots of wide eyes and careful looking at this point!









After I had their interest, I then showed them three other sands and three related rocks.  The white sand here is loaded with calcareous material, and the white "rocks" are pieces of some kind of coral from the same beach.

The green sand is olivine rich, with black chunks of basalt and white pieces of crushed coral.   The green rock is dunite.

The black sand is eroded basalt cinder for the most part, and the black rocks is a basalt with obvious pahoehoe texture on the top surface.












I talked about the three different rocks as representing the three major rock types: the dunite as a metamorphic rock, the basalt as igneous, & the corals as sedimentary.  They didn't quite pick up on the differences or the words well (and I didn't expect them to), but they were at least exposed to the terms.  They liked the basalt the best - it is a pahoehoe sample from Hawaii, so we talked about lava & how it is a hot, liquid rock that cooled to form this solid material.  They were really impressed with that!

Granted the olivine rich sand didn't come from the erosion of dunite, but the samples allowed them to see that there are connections between rocks and sediments.

After we looked at those, we ended with this question: what might happen if you took a sand, and squeezed it really really really hard?  You can't do this with your hands, but the Earth is able to squeeze sands hard enough that they turn back into rocks!  At this point I pulled out a couple of sandstones that are easily seen as grains of sand that are all stuck together.  Minds blown!  That was another moment where their eye-brows were all raised.  Again, here they were exposed to another idea from the bigger concept of the rock cycle.

It was a really fun experience.  These students are considerably younger than the ones I'm used to teaching!  And, if I'm totally honest, they are in general a lot more enthusiastic about learning than some college students!  :-)

Accretionary Wedge #41: Most Memorable Geologic Event I've Directly Experienced: The Eruption of Mt. St. Helens

In the latest call for posts for the Accretionary Wedge, Ron Schott asked geoscience bloggers to relate "the story of the most memorable or significant geologic event that you've directly experienced".

For me that's easy, and yet also difficult.  Easy because there's really only one significant geologic event that I've directly experienced that I'd call memorable & significant, but difficult because I had just turned 6 years old and don't recall a lot of it.  

On the 18th day of the month of May, 1980, the lower 48 states of the U.S. experienced the eruption of Mt. St. Helens.  Obviously when the mountain starts shakin' in a serious way, you don't live to tell about it from up close.  Over 50 people died from the eruption, including one USGS geologist David Johnston who was monitoring the volcano at the time.  He sent word via radio just as the eruption began "This is it!", and gave his life in the study of this mountain.  I lived about 100 miles north of the volcano in a small town called Bremerton, WA.  I don't recall a whole lot about the event, but I do remember watching some of the news reports on TV.  Reports showed video of the ash-clogged & log-jammed streams, snow plows being used to remove the ash from roads, and pictures of entire forests flattened in one direction like matchsticks.  It was amazing.


The mountain had been building up prior to this, with a large bulge on the north flank.  The catastrophic blast of the mountain that day occurred after the bulge over-steepened the hillside and a huge landslide removed material down the mountain, lowering the pressure on the magma below and releasing the main blast.  The blast mainly came out of one side of the summit, the north face of the mountain.

The ash therefore mainly blew northward, but it didn't reach Bremerton.  Instead, the winds took it eastward.  So we never saw any ash where I lived, but one day after the blast my dad decided to drive south.  He collected a small bottle of the ash, which has sat on my shelf for a number of years now and is pictured in these two photographs.

The experiences of geologists from the USGS and the University of Washington monitoring the mountain at the time are documented very well in a CNN video on youtube that unfortunately I can't embed here, but here's the link:  http://www.youtube.com/watch?v=3XYfBxdVDJE  The video is about 7 minutes long and well worth viewing to get a bigger idea of the impact of this eruption.  Also for more info on the blast itself, check out this USGS eruption fact sheet.

GeoPic: Diamond Head Crater

I readily admit I'm not a great photographer, but occasionally I get a shot worth sharing. Here's a picture I took of Diamond Head Crater while on vacation in Hawaii.

The shot was taken from an aircraft (obviously); we were on a commercial flight from Honolulu to Hilo. I had a window seat and was looking north. The clouds parted just perfectly for a moment and I was able to get this shot. My wife and I had just climbed Diamond Head a day or two before, but seeing it from the air was really stunning.

Diamond Head crater is interesting geologically because the volcanic eruptions from this crater, and a number of others like it on Oahu, are much younger than the rest of the island. Most people are aware, I hope anyway, that the Hawaiian Islands were formed as the Pacific plate moved across the top of a hot spot. The hot spot is still active today, producing volcanism on the Big Island. Most of the volcanic rocks of Oahu are between 2-4 million years old. Oahu is now over 200 miles from Kilauea, and the age of the island is consistent with the modern tectonic rate of movement of the Pacific plate at around 9 cm/year. But Diamond Head and a number of other volcanic craters are much younger, less than 500 thousand years old. By this point, Oahu was well beyond the hot spot, and most of Oahu had been undergoing erosion for over a million and a half years! So based on all of this, these young volcanic craters on Oahu are very strange - if Oahu was not over the top of the hot spot anymore, why were these volcanoes erupting? This is a point of current research & debate among geoscientists.