Editing Yellowstone Caldera (section)

=== Second-cycle ===
After ~500&nbsp;kyr of quiescence,{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=236}} a new magmatic system formed north of Big Bend Ridge. It erupted the Bishop Mountain Flow at {{Value|1.4578|0.0016|u=million years}} and the Tuff of Lyle Spring at {{Value|1.4502|0.0027|u=million years}}.{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=229}} The Bishop Mountain Flow is a rhyolite with an exposed volume of about {{convert|23|km3|mi3|abbr=on}} and reaches a thickness of {{convert|375|m|ft|abbr=on}} along the inner caldera wall. The Tuff of Lyle Spring is a {{convert|1|km3|mi3|abbr=on}}, composite ash-flow sheet consisting of two cooling units.{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=226}} Both eruptions appear to have originated from an isolated, highly evolved local magma chamber distinct from the second-cycle magma source.{{sfn|Christiansen|2001|p=64}} Tiffany&nbsp;A. Rivera et&nbsp;al. (2017) suggest these two eruptions should not be assigned to the second cycle but instead represent the separate Lyle Spring magmatic system.{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=236}}
The next pre-collapse rhyolite eruption is the Green Canyon Flow in the north of Big Bend Ridge, with a mapped volume of about {{convert|5|km3|mi3|abbr=on}}, dated at {{Value|1.2989|0.0009|u=million years}}.{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=229}} Its age is indistinguishable from that of the subsequent [[Mesa Falls Tuff]], but the Henry's Fork Caldera fracture truncates the Green Canyon Flow, indicating it predates the second-cycle caldera.{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=234}}

The second-cycle caldera-forming eruption was the Mesa Falls Tuff, dated at {{Value|1.3001|0.0006|u=million years}}.{{sfn|Rivera|Schmitz|Jicha|Crowley|2016|p=7}} Its exposed thickness exceeds {{convert|150|m|ft|abbr=on}} on Thurmon Ridge, though it is likely much thicker within the caldera.{{sfn|Christiansen|2001|p=64}} During the initial Plinian phase, about {{convert|5|m|ft|abbr=on}} of ash and [[pumice]] were deposited around the [[Ashton, Idaho|Ashton]] area, while much of the vitric ash dispersed to more distant regions, as inferred from the high crystal content of the local deposit. This airfall is overlain by a {{convert|1|m|ft|abbr=on}} [[pyroclastic surge]] layer also enriched in crystals.{{sfn|Neace|1986|p=73}} A single cooling unit of ash-flow tuff followed, covering about {{convert|2700|km2|sqmi|abbr=on}} with an estimated volume of {{convert|280|km3|mi3|abbr=on}}.{{sfn|Christiansen|2001|p=64}} The Mesa Falls ash bed (formerly "Pearlette type&nbsp;S") is the distal ash-fall of this eruption, found in [[Brainard, Nebraska|Brainard]] and [[Hartington, Nebraska|Hartington]] in [[Nebraska]], and in the southern [[Rocky Mountains]] of [[Colorado]].{{sfn|Izett|Wilcox|1982}}

Post-collapse eruptions included the Moonshine Mountain dome{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=235}} and five rhyolite domes collectively known as the Island Park Rhyolite.{{sfn|Christiansen|2001|p=66}} The Moonshine Mountain dome, with an estimated volume of {{convert|2.5|km3|mi3|abbr=on}}, erupted at {{Value|1.3017|0.0019|u=million years}}.{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=229}} While its age is indistinguishable from the [[Mesa Falls Tuff]], field evidence indicates it formed after the collapse of the [[Henry's Fork Caldera]].{{sfn|Rivera|Furlong|Vincent|Gardiner|2018|p=235}} The dome's magma source is likely the same region that supplied the Bishop Mountain Flow.{{sfn|Stelten|Champion|Kuntz|2018|p=59}}
The Island Park Rhyolite comprises five bodies: Silver Lake dome, Osborne Butte dome, Elk Butte dome, Lookout Butte dome, and Warm River Butte dome.{{sfn|Christiansen|2001|p=66}} These domes collectively have a total volume of {{convert|1-2|km3|mi3|abbr=on}}.{{sfn|Balsley|Gregory|1998|p=130}} All five erupted within a few centuries, around {{Value|1.2905|0.0020|u=million years}}, during a single eruptive episode.{{sfn|Stelten|Champion|Kuntz|2018|p=55}} While Lookout Butte is located on the rim of Big Bend Ridge caldera wall, the vents for the other four domes align along a northwest-trending, structurally controlled linear vent zone about {{convert|30|km|mi|abbr=on}} long and no more than {{convert|7|km|mi|abbr=on}} wide.{{sfn|Christiansen|2001|p=67}}