Unit D1 Volcanor

The youngest of these rocks are dated at about 220,000 years ago. Rhyodacties and quartz latites in the modern caldera area extruded from about 320,000 years ago to 260,000 years ago, and then silica-rich rhyolites at Glass Mountain northeast of the caldera erupted from about 210,000 years ago to 80,000 years ago. The scattered distribution of the initial mafic eruptions indicates that they were erupted from the mantle, while the slightly younger domes and flows were from a deep-crustal source. The youngest rhyolite eruptions erupted at the northeast rim of the caldera at Glass Mountain and were the first activity of the silicic Long Valley magma chamber (Bailey, et. al., 1989).

Next, we can see that the rock displays a subtle porphyritic texture with plagioclase comprising the phenocrysts. The overall texture of the surrounding groundmass is granoblastic equigranular. Under thin section we also see a weakly defined foliation evidenced in the preferential alignment of actinolite grains and to a lesser extent chlorite grains. Undulose extinction is also observed in quartz indicating the rock was subject to deformation. The normalized quartz, alkali-feldspar, and plagioclase (QAP) values of this rock indicate that it is classified as a grano-diorite according to the IUGS QAPF classification system which is consistent with the hand sample interpretation.

Silicious lava, forced up from deep down below. Soda trachytes extruded in a highly viscous state, building the steep-sides mametons we see in Hanging Rock. And quite young, geologically speaking. Barely a millions years old. (Greene, 11)

One of the major things noticeable from the cross section is that quite a few of the rock layers are over turned, where the older rock layers are above the newer rock layers. This is seen in the contact between the Quartz Monzonite of Papoose Flat and the Campito Formation which is also a disconformity. Next there is some fault zones separating the Camptio, Poleta, and Harkless formations. We then see some more overturned layers with the contacts between Saline Spring Valley Formation (lower and upper members) above the Mule Spring Formation along with some inferred folding. With a normal fault separating the inferred folding event, we see where the overturning occurs. In between the Cambrian layers we see Tertiary Basalt nonconformities also being folded, thus with that we know that the folding event was more recent than the formation of the Basalt. Next there is a large Basalt field with a spot of the Harkless formation. Again we see over tuning as the Basalt field ends there are the Devonian and Mississippian rock Layers on top of the basalt. Separating these overturned layers from the Harkless Formation and the Saline valley Formation (upper member), which are not overturned, is a thrust fault. From this information, there was a major stress event sometime after the Tertiary period causing the rock layers to fold and overturn. And from this stress event and from the folding, normal and thrust faults are formed. Finally we see that there were alluvial and landslide deposits from the Quaternary after the folding, faulting, and over

exciting tell all, focused on the eruptions of Nevado Del Ruiz and Galeras in Northern and

The positive feedback on products to assure quality and may lead to a purchase decision. Endorsements by celebrities and models play an important role in such buying patterns.

the lateral blast, and the large mudflow of this eruption have led to the reassessment

A period of volcanism resulted in igneous intrusions within the Raton Basin-Sierra Grande Uplift Province that was sourced from the upper mantle about 26. 6 billion years ago and is associated with parallel dikes and sills (Higley, 2007). Igneous rocks are common within the Raton Basin and include Tertiary dikes and sills that range in age from 6.7 to 29 5 million years ago (Flores and Bader, 1999). One of the main differences between dikes and sills is that dikes are longer lived magma conduits and sills are features that form when magma is in neutral buoyancy with the surrounding rock (Rooper et al., 2006). These volcanic events are associated with hydrothermal alteration of coal within the basin (Higley, 2007).

Bradbury’s (1967) dissertation research was the first comprehensive study of Zuni Salt Lake maar. Based on a radiocarbon age of 22.9 ± 1.4 ka 14C yr BP (Haynes et al., 1967) on aquatic, calcareous algae from Zuni Salt Lake lacustrine deposits 15 m above the present lake level, he concluded that the Zuni Salt Lake maar formed during the late Pleistocene. This single date provided a maximum age for the Zuni Salt Lake maar but has long been viewed as suspect because of probable hardwater carbon-reservoir effects. Subsequent argon dating of Zuni Salt Lake volcanic rocks resulted in low-resolution plateau ages of 114 ± 38 ka and 86 ± 31 ka (McIntosh and Cather, 1994).

All of the volcanic and metasedimentary rocks are metamorphosed, whose grades are extending from greenschist to upper amphibolite, characterized by low-pressure but high-temperature (Isachsen & Bowring, 1994). The influence of basement fracture zone is reflected in the homoclinal and abruptly alternated trends of the volcanic belts, which is more frequently found in the southwestern domain of the province, while north belts show angular patterns (Fyson & Helmstaedt, 1988; Padgham,1992; Padgham & Fyson, 1992). Except for the sharp dips of the volcanics, regional-scale folds, foliations and cleavages over several successions shown in the metasedimentary rocks are studied to understand the deformation and metamorphism (Isachsen & Bowring, 1994). Fyson & Helmstaedt (1988) compare three major types of folds which are ranked by their ages and sizes from oldest, most extensive F0 to minor-sized, cleavage-foliation-associated S3 folds with intermediate type F1 between them and they suggest that the parallel trend and they suggest both foliation and folds are results of syntectonic

The Raton-Clayton volcanic field is about 20 000 km2 in size, and has been active periodically for the past 9 million years. The area is filled with peaks, cones, and lava-capped mesas. The mesas developed as lava flowed into valleys and depressions, cooled off and formed a resistant top layer over sedimentary rocks. As the surrounding rock eroded, the lava protected the underlying stratigraphy from erosion. This caused todays topography, where that which was once the lowest point, is now the highest. There is some disagreement over why the volcanic field is here, one possible cause is that it is near the end of the Jemez Lineament, which has numerous volcanic centers along its reach, possibly

Lava flows of rhyolite and basalt have flowed through parts of Yellowstone as recently as 70,000 years ago. These lava flows destroyed everything in their paths while moving slowly at a rate of a few hundred feet per day, flowing months, or sometimes even several years. They are thick and cover as much as 130 square miles. They have nearly filled the Yellowstone Caldera, and spilled beyond the caldera’s border. These lava flows are responsible for forming four of the nine named plateaus in

About 7,700 years ago, Mount Mazama erupted on itself after building upon itself and reaching an impressive height of 12,000 feet. The aftermath of the collapse left a crater more than 2000 feet deep and 6 miles wide (Reichmann)! The rocks and minerals from the Mount Mazama

As the eruption wore on, it later produced a phase with red hot pyroclastic surges and flows, along with other volcanic material. This was referred to as the “Peléan” phase. These type of eruptions are known for the mentioned pyroclastic flows, along with hot mud surges. (Universe today) This phase was speculated to have begun during the latter part of the eruption, and is largely regarded as the main killer of most of the surrounding inhabitants. (Museum timeline)

Qfd1 (labeled as Qbws1 on the chart) was found at River Mile 189.5 preserved between a Black Ledge lava dam remnant and a basalt flow. The base of the deposit was 110m above the current river level while the top of the deposit was 170 m above the current river level. The clasts were 92% basalt and had identical Rare-earth element (REE) patterns, which indicated that they came from the same lava dam source. The clasts ranged in size from hyaloclastite ash and lapilli to a 6 m diameter limestone boulder. Based on age and pattern of REE, Qfd1 deposits seemed to have correlated with the dam produced by the Upper Prospect lava flows (Fenton et al. (2004)). While the Toroweap Dam correlated in age to Qfd1, its REE pattern did not align in a parallel