There are numerous potential scientific studies at Santa María and Santiaguito, here listed along with references providing background information.
The chronology of Santiaguito's activity is reasonably well established (Sapper, 1926; Termer, 1934, 1964; Rose, 1973, 1987). The history of Santa María is constrained by the detection of the Mono Lake magnetic excursion in paleomagnetic data on the lavas exposed in the walls of the 1902 explosion crater (Rose et al, 1977a; Conway et al 1993). This correlation suggests that the growth of Santa María's cone was marked by initial high extrusion rates followed by very much slower growth.
The 1902 eruption of Santa María is one of earth's largest historic eruptions (Rose, 1972a). Its tephra deposits can be traced over much of southern Mexico (Williams and Self, 1983). However, there is considerable uncertainty about its volume and the
amounts of distal fallout (Fierstein and Nathanson, 1991; Rose, 1992). The study of Santa María's distal deposits and their distribution represent a way to constrain methods of estimating the proportions of "missing volumes". The 1929 pyroclastic flow from Santiaguito was a deadly eruption with eyewitness accounts and many post eruption photographs (Sapper and Termer, 1930), but the deposits from this eruption, although currently well exposed, have never been studied (Mercado et al, 1988).
Some basic data on the chemical composition, mineralogy and petrography of the lavas of Santa María (Rose et al 1977a) and Santiaguito (Rose, 1972b; 1987) are available and demonstrate the sodic and bimodal character of the volcano's products and the trends toward progressively higher silica with time. Santa María and
Santiaguito represent the southern half of a paired volcano, the northern half being Cerro Quemado, an exogenous dacite dome complex which is chemically quite distinct (Halsor and Rose, 1988; Conway et al, 1992). There has been a limited amount of isotopic study of lavas, focusing on Sr and Nd isotopes (Rose, 1987; Carr et al, 1990), but detailed petrologic studies have not been done.
Petrologic change during eruption:
The 1902 eruption of Santa María represents a magma mixing event between basaltic andesite (52% SiO2) and dacite (65% SiO2) in which mixing was limited and the mafic component was erupted first (Williams, 1979; Williams and Self, 1983; Rose, 1987). No studies of this mixed magma occurrence have been published.
Direct observations of volcanic activity:
Santiaguito has been a laboratory for those interested in studying active eruptions < a href=bib.html>(Reck and von Tuerckheim, 1936, Stoiber et al, 1970; Rose et al, 1977b; 1989a), but, considering the variability and consistency of activity, it has been visited rarely by volcanologists interested in direct observations. A variety of activity (possibly including dome extrusion, active lava flows, avalanching, pyroclastic flows, debris flows of various types and vertical ash eruptions) is likely to be observed during visits of only a few days.
Some studies of patterns of dome growth (Sapper, 1926; Rose 1972b, 1973) have been completed, but work on the structure of Santa María's composite cone, which is so clearly exposed in the 1902 crater, has never been done. The complex morphology of the volcanic basement of Santa María has not been studied at all, although there is some geological mapping of the nearby volcanoes of Siete Orejas (Gierzycki, 1976), Cerro Quemado and Almolonga (Johns, 1975; Conway et al, 1992) and Zuñil (Hughes, 1978).
The vertical ash eruptions that occur on average of several times most days at Santiaguito may be phreatomagmatic and therefore possibly influenced by the infiltration of groundwater. This is an area of heavy monsoonal rainfall amounting to several meters each year. The ashes have a
morphology which suggests that magma-water interaction sometimes takes place (Rose et al, 1980; Heiken and Wohletz, 1985).
Surface Water Hydrology:
This has become an important issue in recent years, because a project for further development of the Río Samala hydroelectric facility is under way, and extensive riverbed aggradation is taking place along the Tambor and Níma II rivers as a result of debris flows. Better hydrologic data on the area is fundamental to accurate hazard assessment.
In recent years the possibility of capture of the Río Nimá II by the Samala river has been forecast (SEAN Bull., 13:11, 1988). This capture would have significant effects on populations far from the volcano.
In recent years the seismicity of Santiaguito has been studied by Guatemalan scientists through the operation of seismic stations. Data on the frequency of volcanic earthquakes, rockfalls and eruptions are available for the past several years. Detailed studies of seismic data could help
illuminate the geometry of the magma bodies below the surface, a focus, also, of petrologic models.
Such work is almost unknown at Santiaguito, although the new volcano observatory hopes to begin a program of this
work. Because of concern about dome collapse, such work is believed to be urgently needed.
Santiaguito has high temperature fumaroles which have
been sites for studies of volcanic gases (Stoiber et al, 1971), gas condensates (Stoiber and Rose, 1972) and fumarolic incrustations (Stoiber and Rose, 1974).
The sulfur dioxide emissions of the volcano have occasionally been measured using a correlation spectrometer (Stoiber et al, 1983; Andres et al, 1993). Satellite thematic mapper remote sensing of Santiaguito's volcanic clouds, and of its thermal anomalies (Andres et al, in review) and the discrimination of lavas of different ages
(Hossli et al, 1992) have also been fruitful.
A preliminary hazard map and report has been completed (Rose et al, 1989b), but much work needs
to be done.
Guatemala's population is concentrated in the proximity of volcanoes that are both highly explosive and frequently active (Sapper, 1927). Work on the communication of of information about volcanic hazards to the local populations within or near the zones of risk has been done by the Guatemalan Comite Nacional de Emergencia (CONE) and needs to be expanded.
There has been very little work in this field, in spite of
the fact that human occupation of the area is known to extend far beyond historic time. A major Olmec archaeological site, Abaj Takalik, is located just south of Santa María
(Graham, 1981). Archaeological materials are found underlying a debris avalanche dated at about 600 AD from Cerro Quemado volcano, a few kilometers N of Santa
María (Conway et al, 1992). Knowledge of the local archaeology of the Santa María area would undoubtedly help us understand the prehistoric activity and allow us to make better hazard assessments.
Stream Aggradation and Volcanic Sedimentation:
Sedimentological studies south of Santa María and Santiaguito have documented the dramatic aggradation of streams (Lentz, 1926; Kuenzi et al, 1979). The effects of this on populations who live along these valleys is dramatic (Rose, 1987; Cobos et al,
1988). Forecasts of the aggradation rates and the consequences are essential to hazard mitigation assessments for the future. Since 1988, erosional rates along the north side of Santiaguito's talus slopes have increased markedly for causes that are not understood
(GVN Bull., 15:3, 1990; 17:5, 1992). This increased erosion supplies materials to feed increased debris flow activity and could lead also to collapse of spine studded domal masses and depressurization of shallow magma.
Ash cloud studies:
The frequent vertical ash explosions have made Santiaguito a fruitful field site for volcanic cloud sampling (Lazrus et al, 1979; Cadle et al, 1979; Rose et al, 1980).
(Bennett, Rose, and Conway, 1992)