Hi Kelsey, Thanks for reaching out to us. I talked with some of the researchers who have visited Katmai caldera lake in recent years, and neither had measured the pH unfortunately. However, the lake is pretty safe to visit, just the usual caveats of backcountry travel in Alaska. As you might know, UAF runs a field trip out there every summer, and they do visit the caldera lake and typically measure its water level each year. There is some hydrothermal activity that originates from the submerged Horseshoe Island, but there isn't a whole lot of degassing going on currently. Researchers in the past have even gone out on the lake in a raft. If you do decide to travel there, it would probably be wise as a routine precaution to measure the pH and temp before sticking hands or anything else in the water! If you do take these measurements, we'd be interested to hear what you find. Here's a photo of the lake from this years' field trip: https://avo.alaska.edu/image/view/196032. As you can see there's still considerable ice cover in June. For your measurements at Kaguyak, our gas research team would be happy if you are willing to share any photos or date/time/location information you can pass on regarding your observations there! If you have photos, please send them to my email at abigail.nastan@alaska.gov as the contact form doesn't allow attachments. Thanks, Abbey Nastan AVO Staff ------------------------------------------------ Hi, I’m trying to find recent data on the pH of the water inside the Mt. Katmai crater lake, but haven’t had much luck. I’d like to visit this lake but I’m not sure how safe it is. So, any data on gas concentrations or other hazards would be extremely helpful too. On another note, I visited Kaguyak and took a few samples to measure the water pH. None of these were highly scientific, as it was just my impromptu curiosity, but I’d like to go back and record more official data next summer. But, of the samples I took at various locations around the crater, the average water pH was 7.3. There was some presence of total chlorine (0.5ppm in 3 of 4 samples), which I found odd. Another thing I noticed was the odor of sulfur near some bubbles coming up from the floor. And the bubbles seemed to be running on a timer; starting and stopping at regular intervals. Anyway, I’d love to hear from you guys! Thank you.