Errata/Addendum for Roadside geology of Mount Rainier National Park and vicinity, Washington Div. of Geology and Earth Resources Information Circular 107, by Patrick Pringle

updated November 7, 2018


Contributors (p. ii): New contact information:

Wendy Gerstel
Qwg Applied Geology
Olympia, WA  98506

Preface, p. iii: I forgot to thank Gene Kiver for contributing information on the summit ice caves including the photo used in Fig. 39 on p. 41. Also Barry Voight reviewed a portion of the text in Leg E. Thanks to both Gene and Barry for their input and assistance.


p. 5. In the center column of the geologic time scale shown, "(Northcraft Formation)" should appear slightly higher after "early Cascade volcanoes erupt as volcanic arc shifts to the west from diffuse Challis arc" and not with sedimentary rocks.

p. 8 typo. Figure 6 caption: In the third from the last sentence it should say "...this stream..." not "...this steam..."

p. 9 typo: "The Cascades volcanic arc has been active for "~40 m.y."   [not 27 m.y., as stated in the book].

Fig. 8 (p. 10): The top of Pyramid Peak (elev. 6937 ft) is located about 1/2 in up and to the right of where the leader points. Tom Sisson of the USGS has reported (2009 email) a revised age for the pumice exposed in Sunset Amphitheater, ~ 165 ka.

Part I

Fig. 14 (p. 18): We inadvertently left out the west Rainier seismic zone (WRSZ) on this figure. However, the WRSZ is shown on Fig. 3 on p. 4 and on Fig. 43, on p. 44.

p. 31 under "Off to an effusive start—Mount Rainier's lavas of 500 to 400 ka":  USGS Geologist Tom Sisson provides a new date for the voluminous pumice deposit on Sourdough Ridge which was originally dated at ~ 380 ka has been revised to ~ 200 ka based on consist Ur-Pb dates on Zircons (Thomas W. Sisson, USGS, written commun., May 13, 2009).

p. 32 under "Another period of accelerated volcanism—Mount Rainier from 280 to 190 ka": USGS Geologist Tom Sisson also notes that a revised date for that pumice and its correlative deposit on Ketron Island noted in Walsh and others (2003) is about 165 ka. (Thomas W. Sisson, USGS, written commun., May 13, 2009)

Fig. 33 caption. after “…reached the Nisqually River”, add “…and that the Osceola Mudflow and Paradise lahars flowed farther than depicted here. The areal extents of the Round Pass Mudflow and Reflection Lakes lahar, both large clay-rich flows, are not shown.”

Part II

Fig. A-3. This crude map of the Tanwax-Ohop valley flood(s) grossly exaggerates the width of the area inundated. Unfortunately an updated map on a lidar base was misplaced; a replacement is in preparation.

Fig. A-6. The Miocene andesite shown in the photo is at La Grande Dam overlook, not Alder Dam overlook.

Fig. A-21. Crystal Mountain shown above Rampart Ridge should be Copper Mountain.

Fig. B-16, p. 73: The leader pointing to the Clear Fork Dacite Flow should extend almost a quarter of an inch (~8 mm) farther down to the flat surface that dips gently to the right.

Fig. C-14, p. 80: Oops, vegetation covers the drift referred to in the caption, so Dear Reader cannot see it!

Fig. D-2 typo. The caption should say “southeast-dipping beds…” (in a future edit of this picture, the farthest right arrow should be changed so that it points to the actual dip slope (which dips to the right in this image) and the other two arrows should be moved slightly so that it’s clear they are pointing to the dip slope and not the scarp slope.

p. 88 (4th page of Leg D): OPTIONAL SIDE TRIP to Mud Mountain Dam. An idea for a ~2 hour field trip is to park at the "horse trailer" parking area, which is a  lot on the east side of the entrance road about halfway in toward the MMD parking area and overlook. The trail descends from the top terrace capped by Osceola Mudflow at an elevation of ~1352 ft (412 m) to a lower terrace at 1220 ft (372m) capped by a normally-graded, lahar-derived gravelly sand (aka "lahar runout", which can be exposed by digging through the vegetation near where you begin descending off the terrace). The gravel road then descends past another lahar runout deposit terrace topping out about 1152 ft (351 m). The deposits of the lower terrace are exposed along the river's right bank and display fragile clasts, normal grading, and other features typical of lahars and lahar runouts. Large accumulations of boulders appear to be what geologists identified as "whale-back bars" at Mount St. Helens. The floodplain of the White River at this site is approximately 1050ft (320m) and river at about 1027 ft (313 m).

Fig. E-10, p. 101: Added information: Steamboat Prow is the pyramidal peak to the right of Emmons Glacier; Inter Glacier sits on upper flank of Steamboat Prow and Winthrop Glacier is above and to the right of the Steamboat Prow; Russell Cliffs (thinly bedded flows dipping to the north) are beyond the Winthrop Glacier.

Fig. F-21, p. 114: The platy jointing alluded to is not easily visible in this photo.

p. 126–128: Tom Sisson of the US Geological Survey reports (person commun., Oct. 25, 2018) that he has a radiometric age on basalt from Hogback Mountain shield volcano of ~ 1Ma.

Fig. H-12, p. 128: The first sentence of the caption should say, “Tumac Mountain shield volcano.” The last portion of the second sentence should be changed to say, “…a crater is hidden in the trees on the west flank of the summit cinder cone.”

The hornblend Spiral Butte dacite flow is mentioned on p. 129 and shown in Fig. H-14. WSDOT engineering geologist Eric Smith has noted a hornblende andesite flowis visisble beneath the dacite flow roughly between MP 154.4 and MP 156.6. The perched nature of the lava flows, likely caused by the their emplacent next to a glacier that later melted, contributes to their lack of stability—A major concern of the engineering geologists. US Geological Survey Geologist Tom Sisson reported to Eric (person. commun., Oct. 25, 2018) the following:

I would say almost certainly yes, they are perched and were probably ice-marginal...We have a K-Ar and a 40Ar/39Ar age for Spiral Butte - the 40Ar/39Ar plateau age is 112.9 +/- 1.8 ka (1 sigma) and the K-Ar age is 103.7 +/-10.2 ka (1 sigma).  This would put the eruption around Marine Oxygen Isotope Stage 5d, when relative sea level was 30 - 60 m below modern values, indicating moderate glacial conditions worldwide (strong glacial conditions have relative sea level about 90 m below modern, and interglacials would be near zero).

Fig. H-24, p. 134: Quaternary Tieton Andesite is the uppermost flow unit shown on the horizon to the far right.

Fig. M-3, p. 156 typo: The third sentence of the caption should say, "The buried trees shown in Fig. M-4 were about 150 ft..."

Leg N. Mi 26.7 [add to end of note] Quiemuth Peak, the highest point in Thurston County at 2922 ft is visible on the horizon at about 11:00 as you descend down the hill. The peak was named in 1993 for the brother of Chief Leschi of the Nisqually tribe. Quiemuth was slain in Governor Isaac Stevens' house in Olympia in 1856 (see ). The mountain is composed of andesite flows of the Eocene Northcraft Formation.


Acknowledgements for assistance w/ typos:

Rich Ambeau, Peter Stein, and others have helped out by spotting typos and errors. Dave Shipley of the Thurston County Historic Commission provided the information about Quiemuth Peak. My thanks to them!

New publications of relevance to Mount Rainier roadside geology
Hammond, P. E., 2017, Geologic map of the northern portions of the Rimrock Lake, Tieton Basin, and western two-thirds of the Weddle Canyon 7.5-minute quadrangles, Yakima County, Washington: Washington Geological Survey Map Series 2017-03, 1 sheet, scale 1:24,000, 19 p. text. [link:]

back to Earth Sciences faculty page

Earth Sciences at Centralia College