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Hannegan caldera

April 14, 2024

Hannegan caldera is a 3.72 million year old volcanic collapse structure in the North Cascades of the U.S. state of Washington.[2] The caldera collapsed during two separate volcanic eruptions that produced as much as 140 km3 of rhyolite ash.[3][4]

South face of Hannegan Peak from Hannegan Pass showing intracaldera structures. A 10-m breccia block is circled.
Outline map of Hannegan caldera in the North Cascades. Postcaldera plutons intrude the southwest portion of the caldera.[1]
The contact between the darker ignimbrite of Ruth Mountain and the pale ignimbrite of Hannegan Peak 1.4 km northeast of Ruth Mountain (skyline) in the Hannegan caldera.[2][1]

The caldera is filled with 55-60 km3 of tuff consisting of ignimbrite,[5] wall-rock breccia,[6] and post-caldera sedimentary rocks.[7] Rocks filling the caldera are lumped into a stratigraphic unit called the Hannegan volcanics.[8][9] This geologic unit is subdivided into the ignimbrite of Hannegan Peak, which is overlain by the slightly younger ignimbrite of Ruth Mountain. Hannegan caldera is centered 8.9 km northeast of Mount Shuksan.[10] Prominent geographic points within the caldera include Hannegan Peak, Hannegan Pass, Ruth Mountain, Icy Peak, the western portion of Copper Ridge and the uppermost reaches of the Chilliwack River. The caldera’s western margin is in Mount Baker-Snoqualmie National Forest but most of the structure is in North Cascades National Park. The caldera is traversed by portions of the Hannegan Pass,[11] Hannegan Peak,[12] Chillwack River,[13] Copper Ridge, and Boundary trails, but most of it is in untracked and rugged mountainous terrain. It is among the best exposed and youngest trap door calderas in the world, and is believed to be the only described double trapdoor caldera on Earth.[2][14]

Geologic history edit

Pre-caldera volcanism and topography edit

The entire region has been deeply eroded by repeated continental and alpine glaciations. No volcanic structures or rocks predating caldera collapse survived multiple glaciations and collapse of the caldera. However, the presence of volcanic rock fragments within the intracaldera tuff are evidence for pre-caldera volcanism, as are dikes outside the caldera margin that have geochemical compositions distinct from rocks related to caldera collapse and later volcanism within the caldera.[1][15][16]

First caldera collapse edit

 
Welded tuff, or ignimbrite, on Hannegan Peak. Knife points to fiamme, pumice clasts flattened by compaction of hot pyroclastic flows.

Around 4 million years ago large volumes rhyolitic magma rose high into the crust. This intrusion most likely caused the surface to dome upwards. Fractures caused by this deformation may have provided conduits for some magma to reach the surface and erupt into relatively small volcanic structures such as felsic and intermediate lava flows and domes, cinder cones, and perhaps small stratovolcanoes. Over 10s or 100s of thousands of years, this upward deformation eventually resulted in a semicircular fracture, or ring fault to form in the brittle crust.[2] This fault encircled the northern margin of the uplifted area and reaching down to the magma chamber, causing sudden release of confining pressure on the magma. Consequently the magma erupted huge volumes of magma as towering columns of volcanic ash and pumice, as well as pyroclastic flows. As the magma emptied, the surface collapsed in a trapdoor fashion down to the north, with the hinge on the south.[14] Though no longer preserved due to millions of years of intense erosion, searing pyroclastic flows must have swept for 10s of kilometers down river valleys beyond the margins of the caldera, incinerating everything in their path. As the surface subsidized a kilometer or more during eruption, volcanic ash filled the resulting horseshoe-shaped caldera. Rock outside the ring fault slid inward as large landslides and left lenses of wall rock breccias and megabreccia interbedded in the tuff filling the collapsing caldera. This tuff, erupted in a single eruption, was lithified and is preserved as the ignimbrite of Hannegan Peak; it is at least 900 meters thick with no base is exposed.[17][9] It is confined within the northern half of the caldera’s structural margin. A relatively precise 40Ar/30Ar radiometric age dates this unit to 3.722 +/- 0.020 million years ago.[2] This northern portion of the Hannegan caldera is confined to the area between Ruth Mountain and Hannegan Peak, and includes the upper most portion of the Chilliwack River valley.

Hiatus and sedimentation edit

 
Fossil Pliocene leaf, 8-cm-long, in intracaldera lake sediment in Hannegan caldera.

Collapse probably took place over a few days. At some time, a lake formed in the depression, and fine grained sediment was deposited on its floor, preserved on the northern flank of Ruth Mountain today as shale and sandstone. These rocks contain fossil leaves, and remain undated.

Second caldera collapse edit

 
Volcanic clasts characterize the ignimbrite of Ruth Mountain. The gray matrix is fine grained volcanic ash erupted during the second collapse of the Hannegan caldera. This outcrop is on the east shoulder of Ruth Mountain. The apple is for scale.

A large volume of unerupted magma remained within the crust, and may have been augmented by subsequent intrusions. After only a brief interval, continued deformation caused the northern ring fault to propagate southward to form an  oblong oval above the remaining magma, which again erupted in another cataclysmic eruption. The southern portion of the caldera then collapsed, this time in a down-to-the-south trapdoor fashion. This formed a ‘double-trap door caldera’, a unique geologic structure. The second portion of the Hannegan collapse was filled with the ignimbrite of Ruth Mountain, exposed from the northeast flank of Ruth Mountain to the southeast flank of Icy Peak to the south. The Ruth Mountain ignimbrite contains many clasts of volcanic rock that predates caldera collapse. This unit must have covered the northern portion of the caldera as well, but was stripped away in that section by erosion. No rock suitable for dating has been found in this unit.

Post-collapse pluton intrusions edit

Two granodiorite magma bodies invaded the Ruth Mountain ignimbrite, and are exposed today as a pair of plutons on Icy Peak and the eastern wall of Nooksack Cirque. The older of these granitic masses is dated to 3.42 million years old, and therefore confines the rock filing the second episode of caldera collapse to the geologically brief 300,000 thousand year interval between the Hannegan ignimbrite (3.72 million years) and 3.42 million years for the pluton. It is likely the Ruth Mountain ignimbrite is much closer to the older age. The second small pluton closely followed, and is 3.36 million years old. Both are part of the Chilliwack Batholith.[8] Mineral analyses from these plutons indicate they cooled at least 1 km below the surface. Yet they are both exposed today due to erosion. They outcrop at the summit of Icy Peak (2156 m) and to within a few hundred feet of the summit of Ruth Mountain (2169 m), the highest point within the caldera. This indicates profound erosion of at least 1 km of intracaldera volcanic rocks in the 3.36 million years since intrusion of these plutons, including any volcanic deposits that may have been associated with the plutons.[18]

The end of volcanic activity in the caldera edit

 
This 240-m thick stack of andesite lava west of Chilliwack Pass in Hannegan caldera is dated to 2.96 million years old. It is the youngest dated rock in the Hannegan volcanics inside the Hannegan caldera. Note geologist in lower left.[2]

Dikes and small rhyolite pods intruded the intracaldera tuff after the caldera collapse was complete. A few small outcrops of andesitic rock are scattered within the caldera, the remnants of lava flows. One sequence of three lava flows exposed on the ridge crest between Ruth Mountain and Chilliwack Pass has a preserved thickness of 240 meters and is dated to 2.96 +/- 0.30 million years old.[2] It is the youngest dated rock unit within the Hannegan volcanics. Following the end of magmatism in the Hannegan area, the focus of magma intrusion and volcanism migrated to the southwest, and sequentially emplaced the Lake Ann Stock (2.75 million years old),[19][20] Kulshan caldera (1.15 million years old),[21] and the numerous vents in the Mount Baker Volcanic field,[22] including the currently active Mount Baker itself.

Comparison with other Cascades calderas edit

The few known Cascade calderas are small and erupted relatively small volumes of ash and ignimbrite.[23][24] Hannegan caldera is only 8 x 3.5 km in outline, with a calculated eruption volume of 55-60 cubic km of magma. Only three calderas have formed in the Cascades since the collapse at Hannegan, and each erupted about the same volume of magma as Hannegan. The Kulshan caldera (1.11 million years old)[21] is 4 x 8 km. The best known and youngest Cascade Range caldera is at 7700 year old Crater Lake, 8 x 10  km.[25][26] The little known 600,000 year old Rockland caldera[27][28] underlies Lassen Peak volcanic center. It is 600,000 years old and is estimated to measure 6 x 6 km. Two other much older Cascade calderas have been sufficiently described in the geologic literature to include here. These are the 21 million-year-old Coquihalla caldera east of Hope, British Columbia, (approx 6 x 6 km)[29] and the 25 million year old Mount Aix caldera (6x9 km)[30][31] 40 km east of Mount Rainier.

See also edit

References edit

  1. ^ a b c Tucker, David S. (2006). "Geologic Map of the Pliocene Hannegan Caldera, North Cascades, Washington". Geological Society of America Digital Maps. doi:10.1130/2006.dmch003.
  2. ^ a b c d e f g Tucker, D.; Hildreth, W.; Ullrich, T.; Friedman, R. (2007). "Geology and complex collapse mechanisms of the 3.72 Ma Hannegan caldera, North Cascades, Washington, USA". Geological Society of America Bulletin. 119 (3–4): 329–342. Bibcode:2007GSAB..119..329T. doi:10.1130/b25904.1. ISSN 0016-7606. S2CID 128417330. ResearchGate:249527328 USGS 70032860.
  3. ^ Hildreth, Wes (2007). Quaternary Magmatism in the Cascades: Geologic Perspectives. U.S. Geological Survey Professional Paper 1744. ISBN 978-1-4113-1945-5.
  4. ^ Haugerud, Ralph A.; Tabor, Rowland W. (2009). "Geologic Map of the North Cascade Range, Washington". U.S. Geological Survey Scientific Investigations Map 2940. Scientific Investigations Map. doi:10.3133/SIM2940. S2CID 128560085. NLA 4761905.
  5. ^ "Mount Baker Volcano Research Center: Eruptive History". Mount Baker Volcano Research Center. Western Washington University. Retrieved 2022-12-11.
  6. ^ Dragovich, Joe D.; Logan, Robert L.; Schasse, Henry W.; Walsh, Timothy J.; Lingley, Jr., William S.; Norman, David K.; Gerstel, Wendy W.; Lapen, Thomas J.; Schuster, J. Eric; Meyers, Karen D. (2002). "Geologic map of Washington—Northwest quadrant". Washington Division of Geology and Earth Resources Geologic Map GM-50. Washington State Department of Natural Resources. OCLC 50325812. Catkey:5683968 MIT Libraries docid:alma990020728850106761. In Schuster, J. Eric; et al. (2011). "Geologic Maps of Washington State" (PDF). Washington Division of Geology and Earth Resources Geologic Maps. Washington State Department of Natural Resources.
  7. ^ Moen, Wayne S. (1969). "Mines and Mineral Deposits of Whatcom County, Washington" (PDF). Washington Division of Mines & Geology Bulletin. 57. United States: Washington Department of Natural Resources. OCLC 75702. OSTI 5309872. S2CID 128474733.
  8. ^ a b Staatz, Mortimer Hay; Tabor, Rowland W.; Weis, Paul L.; Robertson, Jacques F.; Van Noy, Ronald M.; Pattee, Eldon C. (1972). "Geology and Mineral Resources of the Northern Part of the North Cascades National Park, Washington". USGS Numbered Series Bulletin 1359. U.S. Geological Survey: 1-132. ASIN B000NEA2S8. doi:10.3133/b1359. LCCN 72600151. OCLC 768876024. Publication at the NPS History eLibrary. USGS b1359 EPA National Library:1303 309115 UNT key:ark:/67531/metadc304328.
  9. ^ a b Tabor, R. W.; Haugerud, R. A.; Hildreth, Wes; Brown, E.H. (2003). "Geologic Map of the Mount Baker 30- by 60-Minute Quadrangle, Washington". U.S. Geological Survey Miscellaneous Investigation Series (I-2660) (1 ed.). Menlo Park, CA: U.S. Geological Survey. ISBN 0-607-96870-2.
  10. ^ Hildreth, Wes; Lanphere, Marvin A.; Champion, Duane E.; Fierstein, Judy (2004-02-29). "Rhyodacites of Kulshan caldera, North Cascades of Washington: Postcaldera lavas that span the Jaramillo". Journal of Volcanology and Geothermal Research. 130 (3): 227–264. Bibcode:2004JVGR..130..227H. doi:10.1016/S0377-0273(03)00290-7. ISSN 0377-0273.
  11. ^ "Hannegan Pass Trail 674". US Forest Service. Retrieved December 13, 2022.
  12. ^ "Hannegan Pass and Peak". Washington Trails Association. Retrieved December 13, 2022.
  13. ^ Olympic National Park (March 25, 2022). "Copper Ridge / Chilliwack River Trails". National Park Service.
  14. ^ a b Tucker, David S. (2008). "Two-phase, reciprocal, double trapdoor collapse at Hannegan caldera, North Cascades, Washington, USA". IOP Conference Series: Earth and Environmental Science. 3 (1): 012011. Bibcode:2008E&ES....3a2011T. doi:10.1088/1755-1307/3/1/012011. ISSN 1755-1315. S2CID 250683520.
  15. ^ Mullen, Emily K.; Paquette, Jean-Louis; Tepper, Jeffrey H.; McCallum, I. Stewart (2018). "Temporal and spatial evolution of Northern Cascade Arc magmatism revealed by LA–ICP–MS U–Pb zircon dating". Canadian Journal of Earth Sciences. 55 (5): 443–462. Bibcode:2018CaJES..55..443M. doi:10.1139/cjes-2017-0167. hdl:1807/87390. ISSN 0008-4077.
  16. ^ Tepper, Jeffrey H.; Kuehner, Scott M. (May 2004). "Geochemistry of Mafic Enclaves and Host Granitoids from the Chilliwack Batholith, Washington: Chemical Exchange Processes between Coexisting Mafic and Felsic Magmas and Implications for the Interpretation of Enclave Chemical Traits". The Journal of Geology. 112 (3): 349–367. Bibcode:2004JG....112..349T. doi:10.1086/382764. JSTOR 10.1086/382764. OCLC 98228216. S2CID 43130146.
  17. ^ Dennis Martin, Feeney (2008). Timing and Nature of Post-Collapse Sedimentation in Kulshan Caldera, North Cascades, Washington (Thesis). Western Washington University. doi:10.25710/0wqt-v628. OCLC 1030748593. ZNy0YgEACAAJ at Google Books.
  18. ^ Mullen, Emily K. (2011). Petrology and geochemistry of the Mount Baker volcanic field : constraints on source regions and terrane boundaries, and comparison with other Cascade Arc volcanic centers (Thesis). University of Washington. hdl:1773/20946. ProQuest f490cf1f3c2b316b1326e6a819b69707 Academia:75469235.
  19. ^ James, Eric William (1980). Geology and Petrology of the Lake Ann Stock and Associated Rocks (Thesis). Western Washington University. doi:10.25710/r3dp-d443. OL 13589973M.
  20. ^ "Geology and History Summary for Mount Baker". U.S. Geological Survey.
  21. ^ a b Hildreth, Wes (1996). "Kulshan caldera: A Quaternary subglacial caldera in the North Cascades, Washington". Geological Society of America Bulletin. 108 (7): 786–793. Bibcode:1996GSAB..108..786H. doi:10.1130/0016-7606(1996)108<0786:kcaqsc>2.3.co;2. S2CID 129795941. USGS 70018518.
  22. ^ Hildreth, Wes (2003). "Supplemental material: Eruptive history and geochronology of the Mount Baker volcanic field, Washington". Geological Society of America Bulletin. 115 (6): 729–764. doi:10.1130/2003091. In Hildreth, Wes; Fierstein, Judy; Lanphere, Marvin (2003). "Eruptive history and geochronology of the Mount Baker volcanic field, Washington". Geological Society of America Bulletin. 115 (6): 729–764. Bibcode:2003GSAB..115..729H. doi:10.1130/0016-7606(2003)115<0729:EHAGOT>2.0.CO;2. S2CID 140538576. USGS 70025620 ResearchGate:249526873.
  23. ^ Wells, Ray E.; McCaffrey, Robert (2013). "Steady rotation of the Cascade arc". Geology. 41 (9): 1027–1030. Bibcode:2013Geo....41.1027W. doi:10.1130/G34514.1. S2CID 129510320. ResearchGate:256082766 USGS 70117449.
  24. ^ Poland, Michael P.; Lisowski, Michael; Dzurisin, Daniel; Kramer, Rebecca; McLay, Megan; Pauk, Ben (2017). "Volcano geodesy in the Cascade arc, USA". Bulletin of Volcanology. 79 (8): 59. Bibcode:2017BVol...79...59P. doi:10.1007/s00445-017-1140-x. S2CID 133965157.
  25. ^ "Geology and History Summary for Mount Mazama and Crater Lake". U.S. Geological Survey.
  26. ^ Bacon, Charles R. (1983). "Eruptive history of Mount Mazama and Crater Lake Caldera, Cascade Range, U.S.A." Journal of Volcanology and Geothermal Research. 18 (1): 57–115. Bibcode:1983JVGR...18...57B. doi:10.1016/0377-0273(83)90004-5.
  27. ^ Clynne, Michael A. (1990). "Stratigraphic, lithologic and major element geochemical constraints on magmatic evolution at Lassen volcanic center, California". Journal of Geophysical Research. 95 (B12): 19651–19669. Bibcode:1990JGR....9519651C. doi:10.1029/JB095iB12p19651.
  28. ^ Lanphere, M. A.; Champion, D. E.; Clynne, M. A.; Lowenstern, J. B.; Sarna-Wojcicki, A. M.; Wooden, J. L. (2004). "Age of the Rockland tephra, western USA". Quaternary Research. 62 (1): 94–104. Bibcode:2004QuRes..62...94L. doi:10.1016/j.yqres.2004.03.001. S2CID 140689415.
  29. ^ Berman, Robert G.; Armstrong, Richard Lee (1980). "Geology of the Coquihalla Volcanic Complex, southwestern British Columbia". Canadian Journal of Earth Sciences. 17 (8): 985–995. doi:10.1139/e80-099. S2CID 129826748.
  30. ^ Swanson, Donald A.; Haugerud, Ralph Albert, eds. (1994). "Hammond, Paul E., Brunstad, Keith A., and King, John F. Mid-Tertiary volcanism east of Mount Rainier: Fifes Peak volcano-caldera and Bumping Lake pluton- Mount Aix caldera". Geologic Field Trips in the Pacific Northwest. Department of Geological Sciences, University of Washington; Annual Meeting of the Geological Society of America, Seattle, Washington, October 24-27, 1994. OCLC 35377547.
  31. ^ King, John Frederick (1994). Magmatic Evolution and Eruptive History of the Granitic Bumping Lake Pluton, Washington: Source of the Bumping River and Cash Prairie Tuffs (Thesis). Portland State University. doi:10.15760/etd.6649. S2CID 134176687.

Further reading edit

  • Geology of the North Cascades- A Mountain Mosaic – book containing brief geologic descriptions of the Hannegan Pass area, including a sketch view of the Hannegan caldera.

48°52′24″N 121°30′33″W / 48.87333°N 121.50917°W / 48.87333; -121.50917

April 14, 2024
hannegan, caldera, million, year, volcanic, collapse, structure, north, cascades, state, washington, caldera, collapsed, during, separate, volcanic, eruptions, that, produced, much, rhyolite, south, face, hannegan, peak, from, hannegan, pass, showing, intracal. Hannegan caldera is a 3 72 million year old volcanic collapse structure in the North Cascades of the U S state of Washington 2 The caldera collapsed during two separate volcanic eruptions that produced as much as 140 km3 of rhyolite ash 3 4 South face of Hannegan Peak from Hannegan Pass showing intracaldera structures A 10 m breccia block is circled Outline map of Hannegan caldera in the North Cascades Postcaldera plutons intrude the southwest portion of the caldera 1 The contact between the darker ignimbrite of Ruth Mountain and the pale ignimbrite of Hannegan Peak 1 4 km northeast of Ruth Mountain skyline in the Hannegan caldera 2 1 The caldera is filled with 55 60 km3 of tuff consisting of ignimbrite 5 wall rock breccia 6 and post caldera sedimentary rocks 7 Rocks filling the caldera are lumped into a stratigraphic unit called the Hannegan volcanics 8 9 This geologic unit is subdivided into the ignimbrite of Hannegan Peak which is overlain by the slightly younger ignimbrite of Ruth Mountain Hannegan caldera is centered 8 9 km northeast of Mount Shuksan 10 Prominent geographic points within the caldera include Hannegan Peak Hannegan Pass Ruth Mountain Icy Peak the western portion of Copper Ridge and the uppermost reaches of the Chilliwack River The caldera s western margin is in Mount Baker Snoqualmie National Forest but most of the structure is in North Cascades National Park The caldera is traversed by portions of the Hannegan Pass 11 Hannegan Peak 12 Chillwack River 13 Copper Ridge and Boundary trails but most of it is in untracked and rugged mountainous terrain It is among the best exposed and youngest trap door calderas in the world and is believed to be the only described double trapdoor caldera on Earth 2 14 Contents 1 Geologic history 1 1 Pre caldera volcanism and topography 1 2 First caldera collapse 1 3 Hiatus and sedimentation 1 4 Second caldera collapse 1 5 Post collapse pluton intrusions 1 6 The end of volcanic activity in the caldera 2 Comparison with other Cascades calderas 3 See also 4 References 5 Further readingGeologic history editPre caldera volcanism and topography edit The entire region has been deeply eroded by repeated continental and alpine glaciations No volcanic structures or rocks predating caldera collapse survived multiple glaciations and collapse of the caldera However the presence of volcanic rock fragments within the intracaldera tuff are evidence for pre caldera volcanism as are dikes outside the caldera margin that have geochemical compositions distinct from rocks related to caldera collapse and later volcanism within the caldera 1 15 16 First caldera collapse edit nbsp Welded tuff or ignimbrite on Hannegan Peak Knife points to fiamme pumice clasts flattened by compaction of hot pyroclastic flows Around 4 million years ago large volumes rhyolitic magma rose high into the crust This intrusion most likely caused the surface to dome upwards Fractures caused by this deformation may have provided conduits for some magma to reach the surface and erupt into relatively small volcanic structures such as felsic and intermediate lava flows and domes cinder cones and perhaps small stratovolcanoes Over 10s or 100s of thousands of years this upward deformation eventually resulted in a semicircular fracture or ring fault to form in the brittle crust 2 This fault encircled the northern margin of the uplifted area and reaching down to the magma chamber causing sudden release of confining pressure on the magma Consequently the magma erupted huge volumes of magma as towering columns of volcanic ash and pumice as well as pyroclastic flows As the magma emptied the surface collapsed in a trapdoor fashion down to the north with the hinge on the south 14 Though no longer preserved due to millions of years of intense erosion searing pyroclastic flows must have swept for 10s of kilometers down river valleys beyond the margins of the caldera incinerating everything in their path As the surface subsidized a kilometer or more during eruption volcanic ash filled the resulting horseshoe shaped caldera Rock outside the ring fault slid inward as large landslides and left lenses of wall rock breccias and megabreccia interbedded in the tuff filling the collapsing caldera This tuff erupted in a single eruption was lithified and is preserved as the ignimbrite of Hannegan Peak it is at least 900 meters thick with no base is exposed 17 9 It is confined within the northern half of the caldera s structural margin A relatively precise 40Ar 30Ar radiometric age dates this unit to 3 722 0 020 million years ago 2 This northern portion of the Hannegan caldera is confined to the area between Ruth Mountain and Hannegan Peak and includes the upper most portion of the Chilliwack River valley Hiatus and sedimentation edit nbsp Fossil Pliocene leaf 8 cm long in intracaldera lake sediment in Hannegan caldera Collapse probably took place over a few days At some time a lake formed in the depression and fine grained sediment was deposited on its floor preserved on the northern flank of Ruth Mountain today as shale and sandstone These rocks contain fossil leaves and remain undated Second caldera collapse edit nbsp Volcanic clasts characterize the ignimbrite of Ruth Mountain The gray matrix is fine grained volcanic ash erupted during the second collapse of the Hannegan caldera This outcrop is on the east shoulder of Ruth Mountain The apple is for scale A large volume of unerupted magma remained within the crust and may have been augmented by subsequent intrusions After only a brief interval continued deformation caused the northern ring fault to propagate southward to form an oblong oval above the remaining magma which again erupted in another cataclysmic eruption The southern portion of the caldera then collapsed this time in a down to the south trapdoor fashion This formed a double trap door caldera a unique geologic structure The second portion of the Hannegan collapse was filled with the ignimbrite of Ruth Mountain exposed from the northeast flank of Ruth Mountain to the southeast flank of Icy Peak to the south The Ruth Mountain ignimbrite contains many clasts of volcanic rock that predates caldera collapse This unit must have covered the northern portion of the caldera as well but was stripped away in that section by erosion No rock suitable for dating has been found in this unit Post collapse pluton intrusions edit Two granodiorite magma bodies invaded the Ruth Mountain ignimbrite and are exposed today as a pair of plutons on Icy Peak and the eastern wall of Nooksack Cirque The older of these granitic masses is dated to 3 42 million years old and therefore confines the rock filing the second episode of caldera collapse to the geologically brief 300 000 thousand year interval between the Hannegan ignimbrite 3 72 million years and 3 42 million years for the pluton It is likely the Ruth Mountain ignimbrite is much closer to the older age The second small pluton closely followed and is 3 36 million years old Both are part of the Chilliwack Batholith 8 Mineral analyses from these plutons indicate they cooled at least 1 km below the surface Yet they are both exposed today due to erosion They outcrop at the summit of Icy Peak 2156 m and to within a few hundred feet of the summit of Ruth Mountain 2169 m the highest point within the caldera This indicates profound erosion of at least 1 km of intracaldera volcanic rocks in the 3 36 million years since intrusion of these plutons including any volcanic deposits that may have been associated with the plutons 18 The end of volcanic activity in the caldera edit nbsp This 240 m thick stack of andesite lava west of Chilliwack Pass in Hannegan caldera is dated to 2 96 million years old It is the youngest dated rock in the Hannegan volcanics inside the Hannegan caldera Note geologist in lower left 2 Dikes and small rhyolite pods intruded the intracaldera tuff after the caldera collapse was complete A few small outcrops of andesitic rock are scattered within the caldera the remnants of lava flows One sequence of three lava flows exposed on the ridge crest between Ruth Mountain and Chilliwack Pass has a preserved thickness of 240 meters and is dated to 2 96 0 30 million years old 2 It is the youngest dated rock unit within the Hannegan volcanics Following the end of magmatism in the Hannegan area the focus of magma intrusion and volcanism migrated to the southwest and sequentially emplaced the Lake Ann Stock 2 75 million years old 19 20 Kulshan caldera 1 15 million years old 21 and the numerous vents in the Mount Baker Volcanic field 22 including the currently active Mount Baker itself Comparison with other Cascades calderas editThe few known Cascade calderas are small and erupted relatively small volumes of ash and ignimbrite 23 24 Hannegan caldera is only 8 x 3 5 km in outline with a calculated eruption volume of 55 60 cubic km of magma Only three calderas have formed in the Cascades since the collapse at Hannegan and each erupted about the same volume of magma as Hannegan The Kulshan caldera 1 11 million years old 21 is 4 x 8 km The best known and youngest Cascade Range caldera is at 7700 year old Crater Lake 8 x 10 km 25 26 The little known 600 000 year old Rockland caldera 27 28 underlies Lassen Peak volcanic center It is 600 000 years old and is estimated to measure 6 x 6 km Two other much older Cascade calderas have been sufficiently described in the geologic literature to include here These are the 21 million year old Coquihalla caldera east of Hope British Columbia approx 6 x 6 km 29 and the 25 million year old Mount Aix caldera 6x9 km 30 31 40 km east of Mount Rainier See also editDave Tucker geologist References edit a b c Tucker David S 2006 Geologic Map of the Pliocene Hannegan Caldera North Cascades Washington Geological Society of America Digital Maps doi 10 1130 2006 dmch003 a b c d e f g Tucker D Hildreth W Ullrich T Friedman R 2007 Geology and complex collapse mechanisms of the 3 72 Ma Hannegan caldera North Cascades Washington USA Geological Society of America Bulletin 119 3 4 329 342 Bibcode 2007GSAB 119 329T doi 10 1130 b25904 1 ISSN 0016 7606 S2CID 128417330 ResearchGate 249527328 USGS 70032860 Hildreth Wes 2007 Quaternary Magmatism in the Cascades Geologic Perspectives U S Geological Survey Professional Paper 1744 ISBN 978 1 4113 1945 5 Haugerud Ralph A Tabor Rowland W 2009 Geologic Map of the North Cascade Range Washington U S Geological Survey Scientific Investigations Map 2940 Scientific Investigations Map doi 10 3133 SIM2940 S2CID 128560085 NLA 4761905 Mount Baker Volcano Research Center Eruptive History Mount Baker Volcano Research Center Western Washington University Retrieved 2022 12 11 Dragovich Joe D Logan Robert L Schasse Henry W Walsh Timothy J Lingley Jr William S Norman David K Gerstel Wendy W Lapen Thomas J Schuster J Eric Meyers Karen D 2002 Geologic map of Washington Northwest quadrant Washington Division of Geology and Earth Resources Geologic Map GM 50 Washington State Department of Natural Resources OCLC 50325812 Catkey 5683968 MIT Libraries docid alma990020728850106761 In Schuster J Eric et al 2011 Geologic Maps of Washington State PDF Washington Division of Geology and Earth Resources Geologic Maps Washington State Department of Natural Resources Moen Wayne S 1969 Mines and Mineral Deposits of Whatcom County Washington PDF Washington Division of Mines amp Geology Bulletin 57 United States Washington Department of Natural Resources OCLC 75702 OSTI 5309872 S2CID 128474733 a b Staatz Mortimer Hay Tabor Rowland W Weis Paul L Robertson Jacques F Van Noy Ronald M Pattee Eldon C 1972 Geology and Mineral Resources of the Northern Part of the North Cascades National Park Washington USGS Numbered Series Bulletin 1359 U S Geological Survey 1 132 ASIN B000NEA2S8 doi 10 3133 b1359 LCCN 72600151 OCLC 768876024 Publication at the NPS History eLibrary USGS b1359 EPA National Library 1303 309115 UNT key ark 67531 metadc304328 a b Tabor R W Haugerud R A Hildreth Wes Brown E H 2003 Geologic Map of the Mount Baker 30 by 60 Minute Quadrangle Washington U S Geological Survey Miscellaneous Investigation Series I 2660 1 ed Menlo Park CA U S Geological Survey ISBN 0 607 96870 2 Hildreth Wes Lanphere Marvin A Champion Duane E Fierstein Judy 2004 02 29 Rhyodacites of Kulshan caldera North Cascades of Washington Postcaldera lavas that span the Jaramillo Journal of Volcanology and Geothermal Research 130 3 227 264 Bibcode 2004JVGR 130 227H doi 10 1016 S0377 0273 03 00290 7 ISSN 0377 0273 Hannegan Pass Trail 674 US Forest Service Retrieved December 13 2022 Hannegan Pass and Peak Washington Trails Association Retrieved December 13 2022 Olympic National Park March 25 2022 Copper Ridge Chilliwack River Trails National Park Service a b Tucker David S 2008 Two phase reciprocal double trapdoor collapse at Hannegan caldera North Cascades Washington USA IOP Conference Series Earth and Environmental Science 3 1 012011 Bibcode 2008E amp ES 3a2011T doi 10 1088 1755 1307 3 1 012011 ISSN 1755 1315 S2CID 250683520 Mullen Emily K Paquette Jean Louis Tepper Jeffrey H McCallum I Stewart 2018 Temporal and spatial evolution of Northern Cascade Arc magmatism revealed by LA ICP MS U Pb zircon dating Canadian Journal of Earth Sciences 55 5 443 462 Bibcode 2018CaJES 55 443M doi 10 1139 cjes 2017 0167 hdl 1807 87390 ISSN 0008 4077 Tepper Jeffrey H Kuehner Scott M May 2004 Geochemistry of Mafic Enclaves and Host Granitoids from the Chilliwack Batholith Washington Chemical Exchange Processes between Coexisting Mafic and Felsic Magmas and Implications for the Interpretation of Enclave Chemical Traits The Journal of Geology 112 3 349 367 Bibcode 2004JG 112 349T doi 10 1086 382764 JSTOR 10 1086 382764 OCLC 98228216 S2CID 43130146 Dennis Martin Feeney 2008 Timing and Nature of Post Collapse Sedimentation in Kulshan Caldera North Cascades Washington Thesis Western Washington University doi 10 25710 0wqt v628 OCLC 1030748593 ZNy0YgEACAAJ at Google Books Mullen Emily K 2011 Petrology and geochemistry of the Mount Baker volcanic field constraints on source regions and terrane boundaries and comparison with other Cascade Arc volcanic centers Thesis University of Washington hdl 1773 20946 ProQuest f490cf1f3c2b316b1326e6a819b69707 Academia 75469235 James Eric William 1980 Geology and Petrology of the Lake Ann Stock and Associated Rocks Thesis Western Washington University doi 10 25710 r3dp d443 OL 13589973M Geology and History Summary for Mount Baker U S Geological Survey a b Hildreth Wes 1996 Kulshan caldera A Quaternary subglacial caldera in the North Cascades Washington Geological Society of America Bulletin 108 7 786 793 Bibcode 1996GSAB 108 786H doi 10 1130 0016 7606 1996 108 lt 0786 kcaqsc gt 2 3 co 2 S2CID 129795941 USGS 70018518 Hildreth Wes 2003 Supplemental material Eruptive history and geochronology of the Mount Baker volcanic field Washington Geological Society of America Bulletin 115 6 729 764 doi 10 1130 2003091 In Hildreth Wes Fierstein Judy Lanphere Marvin 2003 Eruptive history and geochronology of the Mount Baker volcanic field Washington Geological Society of America Bulletin 115 6 729 764 Bibcode 2003GSAB 115 729H doi 10 1130 0016 7606 2003 115 lt 0729 EHAGOT gt 2 0 CO 2 S2CID 140538576 USGS 70025620 ResearchGate 249526873 Wells Ray E McCaffrey Robert 2013 Steady rotation of the Cascade arc Geology 41 9 1027 1030 Bibcode 2013Geo 41 1027W doi 10 1130 G34514 1 S2CID 129510320 ResearchGate 256082766 USGS 70117449 Poland Michael P Lisowski Michael Dzurisin Daniel Kramer Rebecca McLay Megan Pauk Ben 2017 Volcano geodesy in the Cascade arc USA Bulletin of Volcanology 79 8 59 Bibcode 2017BVol 79 59P doi 10 1007 s00445 017 1140 x S2CID 133965157 Geology and History Summary for Mount Mazama and Crater Lake U S Geological Survey Bacon Charles R 1983 Eruptive history of Mount Mazama and Crater Lake Caldera Cascade Range U S A Journal of Volcanology and Geothermal Research 18 1 57 115 Bibcode 1983JVGR 18 57B doi 10 1016 0377 0273 83 90004 5 Clynne Michael A 1990 Stratigraphic lithologic and major element geochemical constraints on magmatic evolution at Lassen volcanic center California Journal of Geophysical Research 95 B12 19651 19669 Bibcode 1990JGR 9519651C doi 10 1029 JB095iB12p19651 Lanphere M A Champion D E Clynne M A Lowenstern J B Sarna Wojcicki A M Wooden J L 2004 Age of the Rockland tephra western USA Quaternary Research 62 1 94 104 Bibcode 2004QuRes 62 94L doi 10 1016 j yqres 2004 03 001 S2CID 140689415 Berman Robert G Armstrong Richard Lee 1980 Geology of the Coquihalla Volcanic Complex southwestern British Columbia Canadian Journal of Earth Sciences 17 8 985 995 doi 10 1139 e80 099 S2CID 129826748 Swanson Donald A Haugerud Ralph Albert eds 1994 Hammond Paul E Brunstad Keith A and King John F Mid Tertiary volcanism east of Mount Rainier Fifes Peak volcano caldera and Bumping Lake pluton Mount Aix caldera Geologic Field Trips in the Pacific Northwest Department of Geological Sciences University of Washington Annual Meeting of the Geological Society of America Seattle Washington October 24 27 1994 OCLC 35377547 King John Frederick 1994 Magmatic Evolution and Eruptive History of the Granitic Bumping Lake Pluton Washington Source of the Bumping River and Cash Prairie Tuffs Thesis Portland State University doi 10 15760 etd 6649 S2CID 134176687 Further reading editGeology of the North Cascades A Mountain Mosaic book containing brief geologic descriptions of the Hannegan Pass area including a sketch view of the Hannegan caldera 48 52 24 N 121 30 33 W 48 87333 N 121 50917 W 48 87333 121 50917 Retrieved from https en wikipedia org w index php title Hannegan caldera amp oldid 1189379730, wikipedia, wiki, book, books, library,

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