| Pyroclastic Layer | Source Volcano | Approximate Age | Description | Comments |
| X | Rainier | >110-<150 | Scattered pumice lapilli | |
| W | St. Helens | 450 | Pumice ash | Layer W is a white pumice of fine to medium sand size. It thickens from about a quarter of an inch on the west side of the park to about 3 inches near the southeast corner. |
| C | Rainier | >2,150-<2,500 | Pumice lapilli and scattered blocks | Mostly lapilli size and is widely distributed over most of the park east of the volcano. It is generally one to several inches thick. |
| Y | St. Helens | >3,250-<4,000 | Pumice ash | Light yellowish-brown pumice of medium to very coarse sand size. It thickens westward from about 1 inch near the east edge of the park to about 12 inches near the southwest corner. |
| B | Rainier | >4,000-<5,800 | Pumice ash and scattered lapilli | |
| H | Rainier | >4,000-<5,800 | Scattered pumice lapilli | |
| F | Rainier | 5,700 | Montmorillonite-rich lithic ash | |
| S | Rainier | >5,700-<6,600 | Sand-to block-sized lithic rubble | The layer consists of an unsorted mixture of sand, silt, and angular rock fragments as large as 1.5 feet across. |
| N | Rainier | >5,800-<6,600 | Lithic ash | |
| D | Rainier | >5,800-<6,600 | Pumice lapilli | |
| L | Rainier | >5,800-<6,600 | Pumice lapilli | |
| A | Rainier | >5,800-<6,600 | Pumice ash and scattered lapilli | |
| O | Mazama | 6,600 | Pumice ash | This layer blankets the entire park and the adjoining region to a depth of 1-2 inches and is a distinctive yellowish orange. |
| R | Rainier | >8,750-<11,000? | Pumice and lithic lapilli and ash | |
| Modified from: Crandell, 1971, USGS Professional Paper 677, p.12, p.22; table source originally from: D.R. Mullineaux (written commun., 1970) | ||||
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