We headed out and circumnavigated Table Mountain.
The map above shows our route around table (kind of) and the proximity to Mount Baker
Table Mountain is a giant pile of lava that was formed approximately 310,000 years ago. The rock on Table Mountain is called Andesite, a close relative of Basalt. Basalt is in the "igneous rock" family which is formed from melted rock or magma. When the Magma flows out onto the earth's surface (lava), it will quickly crystallize and cool into rock. When this happens, it creates these columns that can look like this:
not table mountain, just an example.
So, fun fact. The reason that Table Mountain has received its namesake is because of the flat top surface from the original thick lava flow. Some geologists actually think that the Table Mountain lava flow was so thick that it must have flowed into a constraining canyon. Also, if you look at Table, you'll see that some of the andesite columns jut out all over the place, and they believe this was caused by a glacier that constrained the flow.
So, here was the view of Mount Baker after we reached the top of Herman Saddle
Table Mountain is the peak to the left, and Mount Baker is in the background
Okay. So, to move away from Table Mountain and Andesite/volcanic remnants, i'll return back to the trail i hate most: Hannegan Pass.
Hannegan Pass was on the path to redemption until we learned about the rock that made up the area. Here's a quick easy to understand description from my book:
As the trail to Hannegan Pas ascends the avalanche-scoured slopes of upper Ruth Creek, the dark cliffs of Mount Sefrit rise impressively across the creek to the southwest. Most of this mountain is underlain by a dark gabbro pluton of the Chiliwack batholith, a rock richer in iron, mangesium, and calcium then most of the other batholithic rocks. The Mount Sefrit gabbro is the slowly cooled, coarse-grained equivalent of basalt and could represent the primordial subduction zone melt that fed the Chilliwack batholith, but without the compositional changes induced by magmatic differentiation. (Geology of the North Cascades - pg. 99)
Yep, that totally made sense.
so, quick definitions (if you haven't figured out yet, this post is more for me trying to understand then keeping your attention)
Gabbro - when basaltic magma crystallizes slowly but without differentiation. The plutonic equivalent of basalt.
batholith - Very large mass of slowly cooled intrusive igneous rock. Must be at least 50 square miles in exposed area
Chilliwack batholith - an area of exposed rock north of the Chilliwack River.
Subduction - Process of one crustal plate sliding down and below another crustal plate as the two converge.
Subduction Zone - the area between the two plates, somewhat like a giant thrust fault.
Magmatic Differentiation - When magma begins to crystallize, the first crystals to form are commonly those of minerals richer in iron, magnesium, and calcium. These are dark minerals (hornblende, pyroxene & calcium rich plagioclase feldspar). As a result, the remaining melt has proportionately less iron, magnesium and calcium and relatively more elements such as sodium, aluminum and silicon. So, when the melt from the magma chamber reaches the earth, it can turn into any of those types of rocks based on whatever stage the magma was in the differentiation process.
WHEW. so, now that entire paragraph on one single section of one trail, kind of makes sense... until you look at this picture and see quartz.
Hannegan Pass was on the path to redemption until we learned about the rock that made up the area. Here's a quick easy to understand description from my book:
As the trail to Hannegan Pas ascends the avalanche-scoured slopes of upper Ruth Creek, the dark cliffs of Mount Sefrit rise impressively across the creek to the southwest. Most of this mountain is underlain by a dark gabbro pluton of the Chiliwack batholith, a rock richer in iron, mangesium, and calcium then most of the other batholithic rocks. The Mount Sefrit gabbro is the slowly cooled, coarse-grained equivalent of basalt and could represent the primordial subduction zone melt that fed the Chilliwack batholith, but without the compositional changes induced by magmatic differentiation. (Geology of the North Cascades - pg. 99)
Yep, that totally made sense.
so, quick definitions (if you haven't figured out yet, this post is more for me trying to understand then keeping your attention)
Gabbro - when basaltic magma crystallizes slowly but without differentiation. The plutonic equivalent of basalt.
batholith - Very large mass of slowly cooled intrusive igneous rock. Must be at least 50 square miles in exposed area
Chilliwack batholith - an area of exposed rock north of the Chilliwack River.
Subduction - Process of one crustal plate sliding down and below another crustal plate as the two converge.
Subduction Zone - the area between the two plates, somewhat like a giant thrust fault.
Magmatic Differentiation - When magma begins to crystallize, the first crystals to form are commonly those of minerals richer in iron, magnesium, and calcium. These are dark minerals (hornblende, pyroxene & calcium rich plagioclase feldspar). As a result, the remaining melt has proportionately less iron, magnesium and calcium and relatively more elements such as sodium, aluminum and silicon. So, when the melt from the magma chamber reaches the earth, it can turn into any of those types of rocks based on whatever stage the magma was in the differentiation process.
WHEW. so, now that entire paragraph on one single section of one trail, kind of makes sense... until you look at this picture and see quartz.
anyway, I'll end this post with one cool piece of information i learned from my geology book:
A black outcrop of rock sticking through the glacier near the summit of Ruth Mountain is made up of black phyllite rubble, now cementer together. This mass of older rock is a remnant of a landslide that slid off the Hannegan Caldera walls when the volcano was erupting. This occurred about 4 million years ago.
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