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Mar 6, 2025 : Alan Chapman Pacific Crest Trail

If Geologic Time Were Measured In PCT Miles, How Long Would Your Life/Thru-Hike Be?

The Earth is a staggering 4,550 million (4.55 billion) years old.  Let’s make this more relatable.  Assume the southern terminus of the PCT represents the Earth forming and the northern terminus is today.  The trail is 2,650 miles long, so each mile translates to 1.7 million years.  The average hiker takes around 2,000 steps per mile, so every step is roughly equal to 1,000 years. At this scale, a retired (age ~65 years) hiker’s life is a little over two inches long.  A hiker taking a gap year after college is just under one inch worth of trail.

Feeling small?  Maybe placing key Earth events in the context of PCT miles will help (see map toward the bottom of this post). Let’s hike north and through time from the Mexican border with each trail mile equalling 1.7 million years.**

 

Deep Time on a Long Trail

The first significant event would be the formation of the Moon at trail mile 29 (4.5 billion years ago), between Lake Morena and Mt. Laguna.  We encounter Earth’s oldest preserved rocks at mile 320, approaching Cajon Pass.  The first fossil evidence shows up at mile 612 (3.5 billion year old algae), as we emerge from the Mojave and begin climbing into the Sierras.

Hiking the PCT 4 billion years ago. The moon would have been much closer to Earth. And the hazards to mitigate would have been kinda different.

We don’t encounter the first animals (sponges) until about 750 million years ago, a significant trail distance later at mile 2213 (near Trout Lake, Washington).  As you approach Snoqualmie Pass (mile 2376; 470 million years ago), you begin seeing the first land plants, which resembled modern mosses and liverworts.  Descending Snoqualmie Pass to the north, you see the first woody stemmed trees (mile 2417; 360 million years ago). 

Between Skykomish and Stehekin, you’d encounter the first dinosaurs (mile 2510; 240 million years ago) and the first mammals (mile 2519; 225 million years ago).  The first flowers appear on the side of the trail just outside of Stehekin (mile 2568; 140 million years ago).  The dinosaurs go extinct 66 million years ago (mile 2612) as you near Harts Pass.

Map of the Pacific Crest Trail, with the timing of key events in Earth history translated to trail miles (base modified from Andrew Alfred-Duggan’s 2018 PCT overview map). Inset map base from Gaia GPS.

You exchange familiar glances with Australopithecus afarensis, an early human relative capable of walking, 2.5 miles from the Canadian border (4 million years ago).  The final mile of the trail is a chilly one, as you encounter about a dozen ice ages, with the most recent ice age ending as the northern terminus monument comes into view (about 19,000 years ago; the final 58 feet of trail).  Now stand close enough to the monument that you could lick it – your existence on Earth is about one tongue length. 

Congratulations, weirdo!  As you stand there with your tongue touching the northern terminus, you’ve completed your thru-hike! The amount of time required to accomplish this feat works out to less than half a millimeter of trail distance.

 

**Note that the precise timing of pretty much all of the events described are controversial and are constantly being refined by the latest science.  One notable example that usually results in geoscience conference-clearing brawls concerns when plate tectonics began. Current estimates range from as old as 4 to as recent as 1 billion years ago, depending on who you ask. If I were to put “plate tectonics begins” on the map, it would plot somewhere between Southern California and Northern Oregon. The point here is that individual events may be off by a few trail miles (i.e. a handful of millions of years).  No big deal, right?

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Alan Chapman
Mar 6th : Alan Chapman
Author Page
Alan Chapman's Bio

Geology professor, ultrarunner, nordic skier, father, PCT class of 2025

Comments 8

  • Jess : Mar 6th

    Alan, you’ve outdone yourself 😂 Truly a unique piece here. Love the thought that went into all the graphics!

    Reply
    • Alan Chapman : Mar 7th

      Thanks Jess – it was super fun to put together!

      Reply
  • Josh Zupan : Mar 6th

    This is sick

    Reply
    • Alan Chapman : Mar 7th

      Thanks Josh – glad you enjoyed it!

      Reply
  • Misty Klement : Mar 6th

    What a fun read! Thanks!

    Reply
    • Alan Chapman : Mar 7th

      Thanks Misty – just saw you’re doing the SHT this September. I looove that trail! Feel free to get in touch if you’d like to chat about the trail and associated logistics more!

      Reply
  • Professor Jellybean : Mar 7th

    You *are* planning to compile this all into a book one day…right? This is awesome! I knew I’d love it. 🙂

    Reply
    • Alan Chapman : Mar 7th

      Thanks Professor Jellybean! I had a feeling you’d enjoy it. The thought had crossed my mind about a book…

      Reply

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