Devils Post Pile and Hot Creek: Aug 7-10, 2023

  • photo of Devils postpile, looking up from below them
  • photo showing bright blue/teal pool with steaming water flowing into the stream
  • photo of lupin flowers
  • photo looking west towards the Sierras from Hot Fish Geological Site
  • photo of tops of hexagonile posts
  • photo showing the hexagonal tops on the side
  • photo of a yellow flower in obsidian rocks
  • photo of fish in hatecher
  • photo of obsidian rock
  • photo of side of an obsidian dome
  • photo of tufas in Mono Lake
  • photo of earthuake fissure
  • photo showing a stream through a valley

The Eastern Sierras provide unique geological and environmental features. On this trip we will see towering columnar basalt, boiling water hot-springs draining into a local stream, an earthquake fissure, and the carbonate tufas of Mono Lake. Hiking will be on Tuesday, Wednesday, and Thursday, with camping Monday, Tuesday, and Wednesday nights.

Registration will open May 1st. If you are planning on staying in a hotel, I recommend you make your reservation now (see Camping and Overnights section).


The map on the right (or below on phones) shows all our locations for the weekend. If you click the icon in the upper left corner, a legend will open for the map.

In this weekend trip, we will visit geologic features around Mammoth Lake/Mammoth Mountain. Destinations include

Camping and overnights

We have a large group campground which is a short drive down a well-graded dirt road.

If any individuals/couples want to find hotel rooms nearby, there will probably be some available in Mammoth Lakes. Prices seem to be in the $120+ range. Here’s a list of hotels near Mammoth Lakes on Google Maps. If you opt for a hotel, you’ll be on your own to find us in the mornings, but we’ll always be within about ten miles from Mammoth Lakes. Cell phone service seems to be good in most areas, especially for texting.

Altitude, weather, daylight, bugs, & bears

  • We will be sleeping and hiking between 6,000 and 8,000 feet. This means you may want to hike slower (there is less oxygen in the air) and sunburns are more likely.
  • Historic average high temperature is around 85°F and low of 53°F. We’re not likely to have heavy rain, but it won’t hurt to bring a light rain jacket in your day pack.
  • Daylight is from around 6:15 AM till 7:50 PM.
  • Some of our locations may have mosquitos. Be prepared to defend yourself with repellent if you tend to get bit.
  • The area is considered bear territory (oh you Cal fans are happy!). This doesn’t mean it’s likely that we will see any bears, but food must be kept safe from bears. Our campsites have bear lockers to store food in. If you have a bear canister for food, it won’t hurt if you bring it, but you shouldn’t have to go out and buy one.


Donations ranges vary from $25 (kids and low/limited income) to $75 (adult) to $100 (for those who desire to contribute a bit more).

Your contribution to our expenses is requested. Please donate based what you can afford, and what you think the trip is worth. Our goal is to provide outings that are affordable to all people, but we hope to cover our expenses and be able to bank a bit of money.

Driving, roads, and cars

  • photo showing a wide dirt road
  • photo showing a one-lane dirt road

Most of the roads are paved, but some are well-graded dirt/gravel roads; about five miles at most. Your basic front-wheel drive sedan car can handle them, although the roads are a bit dusty with mild washboarding.


We’ve tried carpooling before, but it never seems to work out. If you’d like to try to find a carpool, please comment at the bottom of this post, on Facebook, or Meetup.

Weather in Mammoth Lakes area

Click here for August 2022 weather history

Bear Territory?

Yes, there can be bears, but they are rare (kind of like if you visit Stanford).


All of our destinations are within about twenty miles of each other. I’ll provide GPS points for everyone so you can use your favorite app to help you find our destinations

If you’d like to see all the hike maps, I’ve uploaded them all to an AllTrails list; if you’d like to have them on your phone, feel free to download them ahead of time.

Monday, Aug 7th


Monday will be a driving day; we’ll gather in our campsite as people arrive in the later afternoon/evening.

Driving times, depending on traffic and your habits, are estimated by Google as follows:

  • San Francisco/San Jose/Oakland (via Highway 120/395) : 5.5-6 hours.
  • Sacramento (via Highway 50/88/89/395): 4.5-5 hours.
  • Fresno (via Highway 120/395): 4.5-5 hours.
  • Reno (via Highway 395): 3 hours
  • Los Angeles (via Highway 395) 5.5 hours

Once you arrive at the campground, you can relax, set up your tent, and make dinner. We’ll have a short walk to the obsidian dome around 5:00 (it’s right next to the campground).


  • photos showing entrance
  • photo showing van and stream at gated entrance
  • photo showing pine trees in campground
  • photo showing pine trees at campsite
  • photo showing entrance signs at campground
  • photo showing vault toilets

We have Obsidian Flat Group Campground reserved from Monday-Thursday. This is a dry campground with only vault toilets (no running water), but it is a short walk from an obsidian dome we’ll be able to explore in the evenings. The campsite is about 4.5 miles down a well-graded gravel and dirt road–any sedan car should be able to make it.

  • photo of side of an obsidian dome
  • photo of obsidian rock

If anyone has a self-contained camper (RV, van, etc.), they may opt for staying overnight at the Crestview Rest Area on Highway 395 (about six miles from the campground).

The campground does not have water, just vault toilets, so come prepared. There are many picnic tables and bear boxes sprinkled within walking distance of the parking area (this area is considered bear country, so keep your food in these bear-proof lockers).

Crestview Rest Area is located on Highway 395 about 1/2 mile south of Owens River Road, and water and flush toilets are available at the rest area. If anyone has a self-contained camper (RV, van, etc.), you are permitted to stay overnight at the Rest Area if that is your preference. Unfortunately, tents are not allowed in Rest Areas.

Tuesday, August 8th: Devi’s postpile and Mammoth earthquake fault


Prepare breakfast on your own; everyone should be ready to leave by 8:00. Pack a lunch, and bring a day pack because we’ll be on the shuttle for most of our transportation today.

Main hike: Devils Postpile

  • photo of Devils postpile, looking up from below them
  • photo of tops of hexagonile posts
  • photo showing the hexagonal tops on the side

We’ll drive to from the campsite to shuttle bus (around 15 miles and 30 minutes), then board the bus for the drive down into the valley that has Devils Postpile.

Everyone will need to purchase a $15 bus pass. I hope to be able to get reservations in advance for the 9:30 AM bus.

We’ll have two options for hiking: We’ll start with a half-mile hike around the Devils Postpiles (seeing them from below and looking at the glacier paved hexagons from the top); then those who wish a longer hike can extend it to about five miles to hike down to Rainbow Falls.

Bring lunch, snacks, and water on the hike.

The shuttle bus can pick up hikers lower in its route if some folks don’t want to hike all the way back to the beginning. Details will be provided in the morning.

Earthquake fault fissure

After the morning/mid-day hike, we’ll probably be in smaller groups depending on the length of the hike each person/group chooses. After riding the shuttle bus back up the hill, I recommend a stop at the this unique feature of the area.

The area around Mammoth Lakes has multitudes of faults, but this particular fissure is still very open (it opened 550-650 years ago). It’s a nice place to visit, with picnic tables and vault toilets.

Wednesday, August 9th: Hot springs!


Breakfast is on your own, everyone should be ready to leave by 8:30. Today we’ll all be in our own vehicles.

Main hike: Hot Creek Geologic Site

This hike is under two miles; we’ll walk down to the hot spring, then up the stream a bit.

The water at the Hot Creek warm springs is so hot and unpredictable that visitors aren’t allowed into the stream it drains into, nor close enough to touch it. We’ll hike upstream a bit to explore other fumaroles that we can get up close and personal with (I’ll bring thermometers so we can see how hot they are!).

At the end of the hike up the stream, folks can walk back down the stream or take a path up to the road to return to the cars.

Late morning/afternoon options

The afternoon has several options., but our goal will be to visit the fish hatchery and a hot spring

Hot Creek Fish Hatchery

The fish hatchery is run by the California Department of Fish & Wildlife and is open to the public daily from 9:00 AM to 3:00 PM. It is completely self-guided, although I ran into a couple of workers who were inoculating the trout who were happy to talk with me about the hatchery.

It’s a nice walk, maybe a half-mile if you visit all the fish raceways.

Hot springs

There are a few open pool hot springs within a few miles of each other in the area (it’s Forest Service land, so open to anyone for free). There is no guarantee how hot or full each spring may be, but bring a suit if you’d like to explore and soak.

Thursday, August 10th: Mono Lake area on the drive out

Thursday we’ll pack up camp, then drive about 40 miles up Highway 395 to explore the Mono Lake area.

Thursday hikes (like all) are optional: Folks with a longer drive may opt to skip these to get home at an earlier hour.

Tufa towers at Mono Lake

A short hike to explore the tufas on the south side of Mono Lake

Warren Fork Trail

We’ll drive a few miles east on Highway 120 and start at hike at around 9,000 feet. This trail is about 3 miles total, with an elevation gain of around 600 feet, but it’s supposed to be through forested trails, which should help us from getting too hot.

Since we are hiking at a higher elevation, we’ll pay particular attention to not leaving anyone behind, and we’ll do the buddy system so everyone has someone to help if they need to sit down.

Click the image below to see all our hikes on AllTrails.

REI pages with suggestions for camping/bugs/etc.

Conclusions and FAQs

This trip is designed to accommodate the novice hiker; most of the hikes have shorter options, and you can join us on any or all of the hikes/explorations. If you have extra time and want to add this trip to the start/end of a longer trip, please feel free to do so.

We’ll probably have between 10 and 30 people on this trip, so please register once you decide you are joining us. If you have any questions, leave them as comments below if they are generalized, or email me if you have a more personal question. You can also text me at 510-859-8533 (if you want a call back, I’ll probably reply from a phone number that ends in 7035).

The week before the trip I’ll send out my cell phone number to everyone attending. We’ve found that texting is the best way to communicate during trips, since texts go through once each way, but phone calls can get dropped on either end.

Please review our FAQ pages if you have any general questions about our trips.


Registration will open May 1st. If you are staying in a hotel, I recommend making your reservation there now.