Drew T. Downs Johanne Schmith Julie M. Chang Kendra J. Lynn Donald A. Swanson 20250919 spreadsheet Reston, VA U.S. Geological Survey https://doi.org/10.5066/P13AY2GB Drew T. Downs Johanne Schmith Julie M. Chang Kendra J. Lynn Donald A. Swanson Ben Gaddis Ashton F. Flinders 2025 publication Journal of Volcanology and Geothermal Research Elsevier Over 16 days from May 11–27, 1924, there were more than 50 explosions from Halemaʻumaʻu crater at Kīlauea volcano on the Island of Hawaiʻi. These explosions ejected blocks weighing >12,000 kg, as well as extremely fine ash to lapilli size tephra. The greatest thicknesses of tephra were at the summit region of Kīlauea, but some tephra fell on Wood Valley, Pāhala, and Waiʻōhinu to the southwest, with trace ash falling on Hilo to the northeast, along the Hāmākua coast (at Hakalau) to the north, and disrupted rail service to the east between Pāhoa and Makuʻu. The most intense explosions occurred on May 17–18 with plumes going ~10 km high (although many plumes throughout the explosive sequence were <1 km high). These explosions and the resulting tephra deposits were characterized not long after they occurred in the publications of Jaggar and Finch (1924), Stearns (1925), and compiled in the Monthly Bulletin of the Hawaiian Volcano Observatory for May 1924 (see Jaggar, 1924; Gaddis and Kauahikaua, 2021). The explosions were described as phreatic in nature as groundwater interacted with hot wall rock of the conduit after the lava lake drained in February 1924 (Stearns, 1925). We investigated these same tephra deposits ~100 years after they erupted and characterized those preserved within ~3 km of the 1924 vent. We undertook grain size and shape analyses on 202 samples collected from 34 tephra profiles using dynamic image analysis, with a subset of layers from nine tephra profiles used for componentry (200 grains per layer in the 0.5–1 mm size fraction). Additionally, we characterize the average diameters (using the five largest clasts) at 216 locations and measure the average diameters of 2,291 ballistics (largest per ~100 m2 area). Gaddis, B., and Kauahikaua, J., 2021, Views of a century of activity at Kīlauea Caldera—A visual essay, chap. B of Patrick, M., Orr, T., Swanson, D., and Houghton, B., eds., The 2008–2018 summit lava lake at Kīlauea Volcano, Hawai‘i: U.S. Geological Survey Professional Paper 1867, 23 p., https://doi.org/10.3133/pp1867B. Jaggar, T.A., 1924, Journal May 1924 Halemaumau. In: Monthly Bulletin of the Hawaiian Volcano Observatory, v. 12, no. 5, p. 39-55. https://pubs.usgs.gov/publication/70268177. Jaggar, T.A., and Finch, R.H., 1924, The explosive eruption of Kilauea in Hawaii, 1924: American Journal of Science, v. 8, p. 353–374, https://doi.org/10.2475/ajs.s5-8.47.353. Stearns, H.T., 1925, The explosive phase of Kilauea volcano, Hawaii, in 1924: Bulletin Volcanologique, v. 2, p. 193–208, https://doi.org/10.1007/BF02719505. The data were collected as part of a research project into the explosive nature of the May 11-27, 1924, explosive eruptions from Halemaʻumaʻu crater, Kīlauea volcano, Island of Hawaiʻi. Samples were used to quantitatively measure grain size, grain shape, tephra thicknesses, maximum clast sizes, ballistic block sizes, and componentry. 2004 2023 ground condition Complete None planned -155.35740 -155.25529 19.42690 19.35100 USGS Thesaurus Volcanology Volcanic Activity Grain Size Grain Shape Tephra Clast Size Componentry Ash Lapilli Explosive Eruption Lithofacies Ballistics USGS Metadata Identifier USGS:66ad82b1d34e20d4a035915d Geographic Names Information System (GNIS) Island of Hawaiʻi Kīlauea Halemaʻumaʻu crater Kaluapele Southwest Rift Zone East Rift Zone None. Please see 'Distribution Info' for details. None. Users are advised to read the dataset's metadata thoroughly to understand appropriate use and data limitations. Drew T. Downs U.S. Geological Survey - Hawaiian Volcano Observatory Research Geologist mailing address

1266 Kamehameha Ave

Hilo HI 96720 US 808-967-7328 ddowns@usgs.gov No formal attribute accuracy tests were conducted. No formal logical accuracy tests were conducted. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. No formal positional accuracy tests were conducted. No formal positional accuracy tests were conducted. Fieldwork was conducted to describe stratigraphic profiles, measure thicknesses, measure maximum clast sizes, measure ballistic block sizes, and collect samples to analyze grain size and grain shape. A total of 196 locations were measured for total, composite thicknesses of 1924 tephra around the summit region of Kīlauea. Additionally, maximum clast sizes (average of the 5 largest clasts) from 216 locations were measured around the summit region of Kīlauea, as well as ballistic block sizes (dimensions) at 2291 locations. Of the 196 locations measured for total, composite tephra thicknesses, 34 of these locations were measured and described in detail to create tephra profiles, and 227 samples were collected from the tephra layers at these 34 locations for grain size and grain shape analyses by dynamic image analysis (using the CAMSIZER® P4 and X2). A subset of 9 locations of the well-characterized tephra layers (56 layers total) were analyzed for componentry of lithic, juvenile, and altered grains in the 0.5-1 mm size fraction. 2023 We used the CAMSIZER® P4 and X2 instruments (hereafter referred to as the P4 and X2, respectively) to obtain quantitative grain size distributions and shape parameters by dynamic image analysis. Both P4 and X2 instruments have a two-camera setup with a wide-angle camera at their bases and a high-resolution zoom camera to cover as wide a grain size range as possible with a frame rate of 300 frames per second. Both instruments disperse samples from a vibrating feeder to ensure random orientation of grains. The P4 covers sizes ranging from 20 to 30,000 μm analyzing grains as they fall from the feeder in front of the cameras. A large size range from a single sample can be problematic, as larger grains create turbulent fall conditions for finer grains, and fine ash can aggregate into larger clumps that will skew grain size distributions. Therefore, all samples were sieved at 1 mm, with the >1 mm size fraction analyzed using the P4 and the <1 mm size fraction analyzed using the X2. The X2 covers sizes ranging from 0.8 to 4,000 μm and offers higher resolution for this size range than the P4. We used an X2 instrument with an X-jet module using pressurized air to ensure laminar grain transport with optimal dispersal, as well as to help avoid aggregation of fine ash. Grain size distributions obtained from the P4 and X2 instruments were merged using the weighed proportions of the greater and smaller than 1 mm fractions. For this study we use the minimum chord (Xcmin) as the size parameter for all samples, because it is compatible with traditional sieve sizes (CAMSIZER manual, 2020). Grain size distribution statistics were obtained using the GRADISTAT software of Blott and Pye (2001). For quantitative 2D grain shape analysis, we used the mean shape data for half phi (ϕ) grain sizes for each sample (X2 of >1 mm and P4 of <1 mm) and whole sample means of X2 and P4 grain shape data. Resolution of the P4 is 67.3 μm per pixel for the base camera and 11.8 μm per pixel for the zoom camera. Resolution of the X2 is 9.9 μm per pixel for the base camera and 0.8 μm per pixel for the zoom camera. This translates to a resolution of ~173–624,255 pixels per grain for the P4 base camera and ~5,638–20,306,186 pixels per grain for the zoom camera for the 1–30 mm grain size range. Resolution of the X2 are ~31–32,054 pixels per grain for the base camera and ~4348–44,247,784 pixels per grain for the zoom camera for the modeled grains of 62.5 μm to 1 mm. Zoom camera data are favored by the dynamic image analysis software algorithm for fine fractions. Blott, S.J., and Pye, K., 2001, Gradistat: Grain size distribution and statistics package for the analysis of unconsolidated sediments: Earth Surface Processes and Landforms, v. 26, p. 1237–1248, https://doi.org/10.1002/esp.261. CAMSIZER manual, 2020, Manual evaluation software CAMSIZER P4, version 0002: Microtrac Retch GMbH. 2023 Point Point Universal Transverse Mercator 5 0.9996 -153.0 0.0 500000.0 0.0 coordinate pair 0.6096 0.6096 meters North_American_Datum_1983 GRS 1980 6378137.0 298.257222101 The data dictionary for entity and attribute data was constructed for (1) Sample, Size, and Shape Data, (2) Raw Grain Size Data, (3) Raw Grain Shape Data, (4) Tephra Thickness Data, (5) Maximum Clast Size Data, (6) Ballistic Block Data, and (7) Componentry Data from field notes and laboratory reports. The data dictionary is provided on the Description of Terms tab on the excel spreadsheet nd as a csv file. U.S. Geological Survey GS ScienceBase mailing address

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. All trademarks and trade names are the property of their respective owners. Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Digital Data https://doi.org/10.5066/P13AY2GB None 20250919 Drew T. Downs U.S. Geological Survey - Hawaiian Volcano Observatory Research Geologist mailing and physical

1266 Kamehameha Avenue, Suite A-8

Hilo Hawaii 96720 US 808-967-7328 ddowns@usgs.gov FGDC Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998