Reference: Connor, C.B., and F.M. Conway, 2000, Basaltic volcanic Fields, in: H. Sigurdsson, editor, Encyclopedia of Volcanoes, Academic Press, New York, 331-343.

Introduction
Physical Characteristics of Volcanic Fields
Temporal Recurrence Rates
Spatial Patterns
Probability of Future Eruptions
Geologic Structure of Volcanic Fields
Petrogenesis of Basalt Volcanic Fields
Origins of Volcanic Fields
Summary
References

Figure 1: Springerville volcanic field
Figure 2: Yucca Mountain volcanic field
Figure 3: Cima volcanic field
Figure 4: Age range chart for Springerville Volcanic Field
Figure 5: Volcanic events and volume through time, Springerville
Figure 6: Pancake volcanic Field
Figure 7: Big Pine volcanic Field
Figure 8: Mesa Butte Fault and Cones
Figure 9: Models of Dike / Fault association

Table1: Physical characteristics of some basaltic volcanic fields

Often, volcanic activity results in the formation of volcanic fields rather than single large volcanic edifices. Volcanic fields comprise small volcanoes (usually with volumes less than 1 km³), such as cinder cones, maars, tuff cones, tuff rings, small shield volcanoes, and lava domes. These volcanoes are dominantly basaltic in composition and each is produced by a single episode of volcanic activity that can last from several days to a few years, or in rare cases decades. Volcanoes formed during single episodes of volcanic activity, without subsequent eruptions, are referred to as monogenetic. Monogenetic volcanoes are commonly clustered within volcanic fields or may constitute linear chains that follow tectonic structures, such as faults. Volcanic fields also form on the flanks of composite or large shield volcanoes and within calderas, where they are often distributed along rift zones. Over periods of hundreds of thousands to millions of years, monogenetic volcanic activity can result in areally extensive volcanic fields consisting of hundreds to thousands of individual volcanoes and cumulative volumes approaching those of individual composite volcanoes.
 

Studies of volcanic fields are among the earliest works in volcanology. Desmarest mapped the cinder cones of Auvergne, France, around 1766, in the process making one of the first geographically accurate geologic maps and employing what Lyell (1830, page 59) referred to as "minute accuracy and admirable graphic power." One of Desmarest's major contributions was the relative dating of cinder cones in Auvergne using geomorphology of the cinder cones and superposition of lava flows that he carefully correlated to vents where possible. Desmarest's techniques have subsequently been emulated by virtually all volcanologists mapping in volcanic fields. The 1759-1774 eruption of Jorullo volcano, Mexico, in the Michoacán-Guanajuato volcanic field focused additional attention on volcanic fields. Geologists such as von Humboldt, Scrope, and Lyell noted the tremendous number of cones around Jorullo and realized that these cones formed during episodes of activity evinced by the Jorullo eruption. The 1943-1952 eruptions of Parícutin volcano, also in the Michoacán- Guanajuato volcanic field led to more systematic mapping in this area. In his seminal work on volcanoes of the Parícutin region, Williams (1950) conducted petrologic investigations, mapping, and relative dating of volcanoes in this region, resulting in the first comprehensive, modern treatment of basaltic volcanic fields.
 

Recent studies of volcanic fields have employed advancing geochronological, geophysical, and geochemical techniques to describe the rates of activity, longevity, and tectonic settings of volcanic fields. Many of these studies have focused on the distribution and timing of volcanism to better understand the processes that govern magma supply and magma ascent. Numerous studies have considered the development of volcanic fields in terms of their regional neotectonic setting, and the influence of geological structures, such as faults, on vent distribution. Others have focused on the petrologic evolution of volcanic fields through time, attempting to relate changes in petrogenesis to changes in patterns and rates in eruptive activity. Cumulatively, these studies provide substantial insight into the volcanology of basaltic volcanic fields. Increasingly, these insights are used to evaluate the long-term hazards associated with volcanic fields located near cities or sensitive facilities such as nuclear power plants and port facilities. Such long term hazard issues drive the need to improve models of the timing and distribution of eruptions within basaltic volcanic fields.

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Fundamental physical characteristics of basaltic volcanic fields include the number of individual vents, the timing and recurrence rates of volcanic eruptions, the distribution of vents, and their relationship to tectonic features, such as basins, faults and rift zones. Table 1 summarizes the number of vents in some basaltic volcanic fields, their areas, and the age ranges of activity. It is evident that basaltic volcanic fields encompass a wide range of areas, volumes, and longevities. Small basaltic volcanic fields typically contain < 50 vents distributed over < 1000 km². Large volcanic fields contain > 100 vents distributed over > 1000 km². No apparent correlation exists between the number of vents in a volcanic field and its longevity (Table 1). For example, the Springerville volcanic field (Figure 1) contains approximately 400 vents formed within 2 m.y. In contrast, the Yucca Mountain volcanic field (Figure 2) has approximately 30 vents formed over 4 m.y. In these two volcanic fields, as in many others, Plio-Quaternary volcanic activity followed earlier episodes of volcanism in the Miocene and Early Pliocene. Rates of volcanism typically wax and wane over long time periods (> 1 m.y.) in basaltic volcanic fields.

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Determination of the timing of volcanism has been a central issue in the study of volcanic fields. Age determinations for individual volcanic vents are used to estimate temporal recurrence rates of volcanism, sometimes referred to as the intensity of volcanic activity, and to correlate rates of volcanic activity with other factors, such as plate motion, rates of crustal extension, and changes in petrology. Age dating techniques applied to basaltic volcanic fields include relative dating of lava flows using stratigraphy, paleomagnetic age dating, cinder cone geomorphology, and detailed radiometric age determinations of individual vents (Figure 3). Often a variety of dating techniques need to be implemented and linked to geologic mapping in order to delineate the chronology of eruptions within a basaltic volcanic field (Figure 4).
 

Even where excellent age determinations are available, confusion can arise over the definition of the volcanic events used to estimate recurrence rates. Ideally, volcanic events would correspond to volcanic eruptions. However, subsequent volcanic eruptions often obliterate or obscure evidence of previous activity. A more easily implemented definition is based on morphology: an individual cinder cone, maar, or similar edifice represents a volcanic event. Alternatively, volcanic events can be defined as mappable eruptive units, each unit being an assemblage of volcanic products indicating a cogenetic origin from a common vent. This definition can become complicated by the formation of multiple vents during a single episode of activity. For example, three closely spaced vents formed during 1975 eruptions in the Klyuchevskoy Group, Kamchatka, forming the New Tolbachik cinder cones. This alignment of three cinder cones might be considered to represent a single volcanic event. These cones extended an alignment formed by three older Holocene cones, creating an alignment that is about 5 km long. In the geologic record, it would be quite difficult to determine if these cones represent one, two, or six volcanic events. Similar alignments are found in many basaltic volcanic fields.
 

In older, eroded volcanic systems, evidence for the occurrence of vents such as vent buds and breccia zones may constitute volcanic events. In these eroded systems it is clear that the number of dikes reaching the shallow crust can far exceed the number of vents formed at the surface. For example, in the San Rafael volcanic field, Utah, more than 1,700 dike segments are mapped in an area with approximately 60 breccia pipes and buds that are interpreted as vents. Even where detailed mapping is available, grouping dikes and vents in such areas into volcanic events or episodes is problematic.
 

A straightforward method of estimating average recurrence rates of volcanic activity is given by:

where N is the total number of volcanic eruptions or vents, t_o is the age of the oldest event and t_y is the age of the youngest event. Long term average recurrence rates in volcanic fields are typically on the order of 10^-4-10^-5 volcanic events per year (v/yr) (Table 1). These average rates are very low compared to the frequencies of eruptions at individual composite cones. Long term averages smooth out significant variation in recurrence rates that may span comparatively short periods of time (< 100 k.y.). For example, in the Michoacan-Guanajuato volcanic field, Mexico, average recurrence rates since 40 ka are on the order of 2 x 10^-3 v/yr, higher than the long term average. In the Springerville volcanic field, Arizona, recurrence rates reached a maximum of 3-4 x 10^-4 v/yr during peak activity in the field about 1 Ma. In contrast, average recurrence rates of vent formation in the Yucca Mountain volcanic field, Nevada, are on the order of 8 x 10^-6 v/yr during the last 1 Ma. Episodic behavior can produce orders of magnitude variation in eruption recurrence rates compared to long term averages. Currently, a significant challenge is to better delineate the time scales of such episodes.
 

Average recurrence rates of volcanic events are a simple measure of the relative activity in volcanic fields, but more detailed analyses have revealed time trends relating eruption volumes and rates of activity. For example, the cumulative erupted volumes of both basalts and rhyolites in the Coso volcanic field, California, are remarkably linear in time. Hence, successive eruptions occur at time intervals that depend on the volumes of the previous eruptions. This linear relationship has been used to forecast the timing of future eruptions. A similar pattern of activity has been identified in the Springerville volcanic field, Arizona, where the areas of individual lava flows rather than volumes were used to estimate magma output rates, primarily because the highly variable thickness of lava flows make the volume estimates difficult. In the Springerville volcanic field, the rates of volcanic eruptions waxed, then waned during the last 2 m.y. but the cumulative area impacted by eruptions remained constant during much of the time prior to 0.3 Ma, despite major changes in the geochemistry of the basalts (Figure 5).

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The episodic character of small-volume basaltic volcanism is further revealed by spatial patterns in vent distributions common to nearly all basaltic volcanic fields. Studies of spatial patterns of vent distribution in volcanic fields have revealed: (i) shifts in the locus of cinder cone volcanism are a common phenomenon in volcanic fields; (ii) cinder cones cluster within these fields, often on several scales; and (iii) vent alignments are ubiquitous, including short local alignments of several vents and more regional alignments that are usually more than 20 km in length and consist of numerous vents. These spatial patterns exist because recurrence rate is often not uniform across a volcanic field even if volumetric output in the field as a whole is steady-state. Various density estimation techniques are used to delineate and characterize spatial patterns in basaltic volcanic fields.
 

Large-scale shifts in the locus of volcanism have been observed in numerous volcanic fields. For example, Plio-Quaternary volcanism in the Pancake volcanic field (Figure 6) has shifted from SW to NE through time, creating an elongate volcanic field that parallels many local Basin and Range structures. This trend in the Pancake field extends Miocene-Early Pliocene volcanic activity in the Reveille Range southwest of Pancake, now preserved as dikes and eroded vents. Similar shifts in activity through time have been observed in the San Francisco, Springerville, Coso, Cima, and Camargo volcanic fields. In some of these volcanic fields, shifts can be related to regional tectonic processes such as plate motion. In other areas, however, shifts in the locus of volcanism seem independent of regional tectonic processes.
 

Vent clustering is a widely recognized phenomenon in volcanic fields. Vent clusters occur on several scales. In the Michoacan-Guanajuato and the Springerville volcanic fields (Figure 1), vent clusters consist of 10-100 individual vents and have diameters up to 50 km. In smaller volcanic fields, statistical methods can delineate clusters of 1 to 10 vents. In some volcanic fields, volcanic activity within clusters waxes and wanes on short time scales compared to the volcanic field as a whole. In other areas, recurrent volcanism occurs within individual clusters over most of the history of the volcanic field.
 

A simple explanation for vent clustering is that magma supply varies across volcanic fields. Mantle rocks beneath vent clusters are close to their solidus and produce melts more readily in response to small changes in the thermo-physical or geochemical state the mantle. Magma in these areas can be generated repeatedly in response to episodic extension or heating as long as the fraction of partial melting is sufficiently small that the source region of the magma is not depleted substantially as a result of repeated melt generation. The scale and longevity of vent clusters, therefore, may reflect the scale of geochemical, temperature and pressure variations in the mantle source region. An alternative explanation is that crustal structures are somehow responsible for the development of clusters. However, the distribution of clusters in most volcanic fields does not directly correlate with the distribution of faults or other features which may ease magma transport through the crust. Although vent alignments and individual vents within clusters often occur near or on faults, fault densities are rarely high within vent clusters compared to nearby areas.

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Spatial patterns and temporal recurrence rates may be combined to estimate probabilities of future volcanic activity within volcanic fields. The probability of future volcanic eruptions within some small area within a volcanic field, Dx, Dy, during some time interval, DT, can be estimated as:

where l _t is the temporal recurrence rate and  l_r is a spatial weighting factor. Both  l_t and  l_r are usually estimated from past patterns of volcanic activity. This equation can be integrated over some larger area than x, y to estimate the probabilities of volcanic eruptions within all or part of the volcanic field while still capturing smaller scale variations in recurrence rate, or integrated over some long period of time. Alternatively, probability of volcanic eruptions may be contoured across the volcanic field.

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Geologic structure of volcanic fields

Alignments of basaltic vents are common in volcanic fields, on shield volcanoes, and in calderas. These alignments and their related structures are used to infer the presence and orientation of subsurface dikes and dike sets, as indicators of crustal stress orientation, and to infer mechanisms of shallow dike injection in active volcanic areas (Figure 7). In active Holocene volcanic fields, such as Craters of the Moon, Idaho, the Laki fissures, Iceland, and the south flank of Tolbachik, Kamchatka, a strong correlation has been recognized between structural trends (faults and fractures) and volcanic alignments consisting of contemporaneous cinder cones associated with single episodes of dike injection. Development of volcano alignments has also been increasingly important in the assessment of long-term volcanic hazards because of the comparatively large map extent of these features.
 

Distinguishing alignments in basaltic volcanic fields comprising hundreds of vents is problematic, however, because aligned vents are often interspersed among a greater number of unaligned cones. Recently, statistical methods have been used to identify vent alignments and improve the ability to discriminate these features objectively (Figure 1). Vent alignments delineated by statistical methods typically parallel regional and local structures, which suggests that vent alignments can form because ascending magmas exploit pre-existing structures repeatedly during separate episodes of activity (Figure 6, Figure 7, Figure 8).
 

One explanation for the occurrence of volcanic vents along faults is that during ascent a dike may abandon its course perpendicular to the least principal stress in favor of a more energy-efficient path along a pre-existing joint or fault. This effect can be modeled in two-dimensions treating the country rock as a uniform, linear-elastic, brittle rock that fractures at some tensile stress level, s_o. The stress needed to create an open vertical fracture in the undeformed rock is:

where s₃ is the least principle in situ stress and s_d is the additional stress needed to deform the fractured host rock to create an aperture. Where a pre-existing fracture exists, dipping at angle , the stress required to dilate this pre-existing fracture is:

where s₁ is the greatest in situ principal stress. A dike will exploit the pre-existing fracture when s_f < s_v. Using a range of appropriate bounding values, the minimum fracture dip a dike is likely to follow at a depth of 10 km is between 75 and 86.The minimum exploitable dip decreases at shallower depths. Stress effects near the earth surface may cause a dike to break out of a fault zone at shallow depths. Such near surface effects become important at a depth of about 500 times the dike width.
 

In three dimensions, the orientation of a fault relative to s₃ plays an essential role in determining whether a fault zone is likely to dilate in response to dike injection. Faults oriented roughly perpendicular to s₃ are termed high-dilation tendency faults and are more likely to provide low-energy pathways to the surface than faults of other orientations. Considering these factors together, vent alignments may form in response to a variety of fault geometries (Figure 9).
 

Faults and dikes are further interrelated because faulting and dike injection play a similar role in accommodating crustal stress, by slip in the case of faults and increased total crustal volume in the case of dikes. In some areas, topography related to faults is suppressed near volcanic fields and individual vent alignments because stress is accommodated by dilation of the crust during dike injection rather than by fault slip. This relationship can explain much of the variation in structure of volcanic fields. For example, cinder cone alignments are common in low volume, low density volcanic fields (e.g., Figure 2 and Figure 7). In larger volume basaltic volcanic fields, like the Springerville volcanic field (Figure 1), mapped faults are rare and cinder cone alignments, though present, are less pervasive. In the former case, rates of dike injection are not sufficient to fully accommodate crustal stress. As a result, fault systems continue to experience slip and dikes tend to parallel or inject into these fault systems. In the latter case, rates of dike injection are sufficient to completely accommodate regional tectonic stresses within the volcanic field. This equalizes, or nearly equalizes, the magnitudes of principal horizontal stresses and their orientations may vary substantially across the volcanic field and over time. Thus, vent alignments are less common in volcanic fields with comparatively high rates of volcanic activity.
 

The linear or nearly linear behavior of total eruptive volume through time (e.g., Figure 5) has suggested a link between crustal strain rate and volcanic activity. If crustal strain rates are relatively uniform over a long period of time and melts are produced by decompression in response to extension, then a direct relationship between crustal strain rate and volume eruption rate should exist. Conversely, changes in the strain rate may result in changes in the rate of volcanic activity. If such a relationship between crustal strain and volcanism recurrence rates proves correct, estimates of volcanic hazards associated with basaltic volcanic fields might be substantially improved by accurate measurements of variation in crustal strain.

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Basaltic volcanic fields are volumetrically dominated by basaltic (< 52 wt. % silica) and basaltic andesite lavas (52 wt % to 56 wt %). The importance (i.e., volume) of more-evolved andesitic to rhyolitic lavas varies considerably from field to field. For example, the San Francisco volcanic field has erupted substantial volumes of evolved lavas that crop out in seven large silicic domes (dacite through rhyolite composition) and the voluminous (= 100 km³), andesitic San Francisco Peaks composite volcano. In sharp contrast, the Springerville volcanic field, which lies just south of the San Francisco field, erupted few intermediate lavas.
 

Basaltic lavas in volcanic fields display a broad range of petrographic features: with every possible gradation from vesicular to non-vesicular, aphyric to porphyritic, and wholly crystalline to glass rich lavas. In most cases, phenocryst phases of mafic lavas comprise, in widely variable proportions, olivine, plagioclase, clinopyroxene, and less commonly orthopyroxene and magnetite. The groundmass of most basalts is typically dominated by the same phases accompanied by titaniferous magnetite, apatite, sparse ilmenite and spinel, and frequently basaltic glass.
 

Basalt magmas originate from partial melting of a lithospheric mantle or asthenospheric source material; the most frequently named parent materials are peridotite and eclogite. Regardless of the source composition, basaltic magmas erupted onto continents are required to rise through substantial thickness (approximately 20 to 45 km) of continental crust before erupting. The compositional variability in basaltic volcanic fields can be explained by some combination of:
 

1) Variable degrees of partial melting of various garnet-bearing upper-mantle sources

2) Mixing of at least two components in the source region of the mantle

3) Fractional crystallization in the deep crust

4) Assimilation of crustal material with concomitant fractional crystallization.
 

Geochemical analyses confirm that the short-lived, monogenetic nature of cinder cones precludes the involvement of long-lived shallow basaltic magma reservoirs beneath basaltic volcanic fields.
 

The variety of mafic rocks erupted in basaltic volcanic fields is exemplified by the San Francisco volcanic field. This field comprises a broad spectrum of mafic lavas, including: basanite, alkali olivine and tholeiitic basalts, and basaltic andesites. Chemically, lavas range from strongly nepheline-normative to quartz-normative basalts. While the locus of basaltic volcanism in the San Francisco volcanic field migrated, broadly, from east to west, extensive sampling and geochemical analysis (including 1000 major and 200+ trace element analysis does not show any evidence of a corresponding systematic spatial or temporal change in basalt lava composition. Remarkably, a single cinder cone cluster, SP cluster which comprises just 60 Early Pleistocene through Holocene basaltic vents, shows a breadth of mafic geochemistry comparable to that of the entire field.
 

Overall, field-wide geochemical trends have been identified in some volcanic fields (e.g., Eifel, Big Pine, Springerville) that can be related to changing source conditions. Elsewhere (e.g., Michoacan-Guanajuato and Cima volcanic fields) temporal and spatial trends in geochemistry are indistinct. Rather, geochemistry of basalts from these fields appear to reflect the natural variability in steady-state, low-volume, basaltic magmatic systems.

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Early ideas on the formation of volcanic fields often involved widespread partial melting with ascending magmas relying on structures to serve as low energy pathways to the surface. In such a model, rates of volcanic activity would be governed directly by crustal processes, rather than rates of melt generation. The origin of this idea is easy to understand - in many volcanic fields the crust appears to have leaked basalt from every conceivable fault and fracture. However, this idea is not consistent with the petrogenesis of basaltic volcanic fields, which almost always involves low rates of partial melting and melt production from a variety of levels in the lithosphere, asthenosphere or both. These melts do not have long residence times in the crust or upper mantle, waiting for tectonic processes to ease their ascent and ultimate eruption. Instead, current evidence indicates that distributed basaltic volcanism is a natural consequence of ongoing low rates of magma production. Nonetheless, rates of extension or subduction are involved, as these rates can play a critical role in rates of partial melting.
 

Fedotov (1981) offered a thermo-physical model for distributed clustered volcanic fields based on his observations in the Kluychevskoy Group. Fedotov suggested that central volcanoes such as composite cones develop when magma supply is sufficient to maintain a thermal anomaly about a central conduit. This conduit provides a low energy pathway to the surface as long as the thermal anomaly persists. In volcanic fields, magma supply rates are so low that such a conduit is not maintained between volcanic eruptions; new ascending magma batches find their own path to the surface, with no opportunity to accumulate in shallow crustal magma chambers. Thus, low rates of heat transfer due to low rates of magma production lead to distributed volcanic fields. Takada (1994) augmented this model by suggesting that rates of extension also play a role. Numerical and physical analog experiments indicate that crack and dike coalescence is more likely within lithosphere that is experiencing low rates of extension compared to lithosphere experiencing high rates of extension. Therefore, Takada (1994) suggests distributed volcanoes are more likely to occur in areas of high strain rate due to the decreased opportunity for dike interaction and coalescence of magmas in crustal magma chambers. Thus, bimodal volcanism can develop in volcanic fields in response to changes in rates of magma production, extension, or both. Cumulatively, the work of Fedotov (1981) and Takada (1994) provides a mechanistic basis for the observation that low rates of magma production and high rates of extension result in formation of volcanic fields rather than central volcanoes.

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Basaltic volcanic fields vary in size, total volume, longevity, and rates of eruptive activity. Commonality among volcanic fields is found in their low rates of magma production, clustered vent distributions, and petrogenesis dominated by mantle, rather than crustal, processes. Delineation of the timing of volcanism, petrologic evolution, and neotectonic setting of volcanic fields involves detailed investigation, a formidable undertaking given of the large number of vents in most basaltic volcanic fields. The interplay between magma production and the neotectonics of the brittle crust exerts a strong control on development of volcanic fields, indicating that such comprehensive study is necessary. Although volcanic fields are characterized by low average rates of magma production, current data indicate that most volcanic fields experience dramatic changes in rates of vent formation and vent distribution over periods of 100 k.y. or less. As geophysical and geochronological techniques develop, it should become possible to delineate episodes of activity in volcanic fields with greater resolution and to relate such episodes to regional tectonics. This degree of resolution will enable volcanologists to move toward a more deterministic understanding of the processes governing the evolution of volcanic fields.

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Arculus, R.J., and Gust, D.A., 1995, Regional petrology of the San Francisco volcanic field, Arizona, USA. Journal of Petrology, v. 36, p. 827-861.
 

Bacon, C.R. 1982. Time-predictable bimodal volcanism in the Coso Range, California. Geology

10: 65-69.
 

Condit, C.D., and C.B. Connor. 1996. Recurrence rates of volcanism in basaltic volcanic fields:

An example from the Springerville volcanic field, Arizona. Geological Society of America Bulletin 108: 1,225-1,241.
 

Connor, C.B., and B.E. Hill. 1995. Three nonhomogeneous Poisson models for the probability of basaltic volcanism: Application to the Yucca Mountain region, Nevada, U.S.A. Journal of Geophysical Research 100(B6): 10,107-10,125.
 

Conway, F.M., C.B. Connor, B.E. Hill, C.D. Condit, K. Mullaney, and C.M. Hall. 1998. Recurrence rates of basaltic volcanism in SP Cluster, San Francisco volcanic field, Arizona, Geology, 26: 655-658.
 

Dohrenwend, J.C., S.G. Wells, and B.D. Turrin, 1986. Degradation of Quaternary cinder cones in the Cima volcanic field, Mojave Desert, California. Geological Society of America Bulletin 97: 421-427.
 

Duffield, W.A., C.R. Bacon, and G.B. Dalrymple. 1980. Late Cenozoic volcanism,

geochronology, and structure of the Coso Range, Inyo County, California. Journal of Geophysical Research 85(B5): 2,381-2,404.
 

Fedotov. S.A. 1981. Magma rates in feeding conduits of different volcanic centers. Journal of Volcanology and Geothermal Research 9: 379-394.
 

Hasenaka, T., and I.S.E. Carmichael. 1987. The cinder cones of Michoacan-Guanajuato, central Mexico: Petrology and chemistry. Journal of Petrology, 28: 241-269.
 

Ho, C.-H., E.I. Smith, D.L. Feuerbach, and T.R. Naumann. 1991. Eruptive probability calculation of the Yucca Mountain site, USA: Statistical estimation of recurrence rates. Bulletin of Volcanology 54: 50-56.
 

Lyell, C. 1830. Principles of Geology, Volume 1, First Edition, reprinted 1990 by University of Chicago Press, Chicago, 511 pp.
 

Mertes, I., and H.-U. Schmincke. 1985. Mafic potassic lavas of the Quaternary West Eifel volcanic field. Contributions in Mineralogy and Petrology, 89: 330-345.
 

Ormerod, D.S., N.W. Rogers, and C.J. Hawesworth. 1991. Melting of the lithosphere mantle: Inverse modeling of alkali-olivine basalts from the Big Pine volcanic field, California. Contributions to Mineralogy and Petrology 108: 305-317.
 

Schmincke, H.-U., V. Lorenz, and H.A. Seck. 1983. The Quaternary Eifel volcanic fields, in: Plateau Uplift, K. Fuchs, editor, Springer-Verlag, Berlin, 139-150.
 

Takada, A. 1994. The influence of regional stress and magmatic input on styles of monogenetic and polygenetic volcanism. Journal of Geophysical Research 99: 13,563-13,574.
 

Tanaka, K.L., E.M. Shoemaker, G.E. Ulrich, and E.W. Wolfe. 1986. Migration of volcanism in the San Francisco volcanic field, Arizona. Geological Society of America Bulletin 97: 129-141.
 

Williams, H. 1950. Volcanoes of the Parícutin Region. U.S. Geological Survey Bulletin, 965B: 165-279.

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