Hot and Bothered on the Lakeshore Trail

Taylor as a scale for some metamorphic rocks (schist).

Mike being a field geologist.

The summer began with a wilt as Mike (a soon-to-be second year grad student in our lab, he ran in the Olympic trials 4 years ago so we call him our olympian) and his field assistant Taylor (an amazing undergrad from Carleton College in Minnesota) stepped off the Lady of the Lake ferry onto the campsite/trailhead at Prince Creek.  This name may sound familiar to you- it was where I was based out of for about half of my MS research.  The site of many adventures, including the Bible believing Christian with a handgun episode (shot a doe in the campground).  Ahh. Good times. 

Our initial plan was to hike into the high country from here (about a 5000 foot gain) and work up high for 6 days.  The snow precluded this plan but I was undaunted and decided we should geologise the so-called Lakeshore trail instead.  This trail runs about 18 miles from Prince Creek to Stehekin, a unique town at the head of Lake Chelan.  Stehekin is only reachable by the Lady of the Lake ferry or by airplane, you can’t drive there.  I will say more on this place later, but trust me, it’s a treasure. 

The forecast for our journey was in the 100s and due to a series of forest fires in the last 10 years, most of this trail has been burned, resulting in a distressing lack of shade.  I can sum up the trip by saying that is was hot.  Very very hot.  We saw some nice rocks and took some good data, but when they say “Lakeshore Trail” I’m sure you imagine happily skipping along the lake shore. Not really, you spend 95% of the trip about 500 feet above it, looking longingly at its icy waters. 

Perhaps my favorite memory of the trip was when we met ANOTHER set of “Bible-believing Christians” or “Young Earthers”.  This didn’t come out immediately, but eventually they both admitted to being preachers (who isn’t in those churches?). They were VERY interested in how old the rocks were. “90 million years you say?”…  The best part was when I admitted to being an atheist- they were visibly taken aback.  Perhaps if I had said I worshipped Satan they would have been more comfortable…

The white stuff is pegmatite, it has BIG crystals.

Most of the rocks we saw were called pegmatite.  A fun word to say, but honestly pegmatite isn’t useful for much in my book.  When magma cools deep in the Earth’s crust you get what is called a pluton.  Plutons are essentially made of granite, so the Sierra Nevada is a series of plutons. So the magma is intruded into the crust and starts cooling and making crystals. Great.  The trick is magma is made up of many different things- iron, magnesium, calcium, silicon, oxygen, etc.  Some of these things are compatible and some are incompatible.  Compatible elements make minerals- these form the granite.  Incompatible elements get rejected from the mineral party and are like the leftovers at a buffet- stuff like water,CO2, and some funky elements.  At the end of the crystallization you’re left with these enriched juices of incompatible elements.  This is what pegmatite is made of- the leftover juices of pluton crystallization.  These fluids then shoot through the pluton and form coarse grained planes called dikes.  Pegmatite is useful to many people- gold is incompatible and can be found in pegmatite. No gold in these pegmatites, though.  Because they are the leftovers, they aren’t usually very insightful for what I’m interested in, which is the pluton part.

Anyway.  Lesson over. Many thanks to Mike and Taylor for suffering through that trip.