Search USGS⌕ Search

Geology topics

H.C. Claassen

Publications and source records attributed to H.C. Claassen.

13 recordsLinked to original sources
USGS1995

A possible deficiency in estimates of wet deposition obtained from data generated by the NADP/NTN network

A conventional precipitation scavenging model is used to evaluate the effect of the performance of a wet-deposition collector on the reported deposition amounts. Three National Atmospheric Deposition Program/National Trends Network sites in semi arid western Colorado were chosen to evaluate chloride and sulfate wet deposition. Observations of the performance of a wet-deposition collector have demonstrated a delay in opening and cycling during a precipitation event. A significant fraction of wet deposition may be excluded when small amounts of initial precipitation are not sampled and a potentially large fraction of annual wet deposition may be excluded if a majority of precipitation events are small. The actual amount missed depends on the precipitation intensity, variability of intensity with time, raindrop or snowflake size and the individual performance characteristics of the collector. Detailed performance data are needed for individual wet-deposition collectors before accurate estimates of wet deposition can be expected.

Atmospheric Environment↗
USGS1994

Specific surface area of a crushed welded tuff before and after aqueous dissolution

Specific surface areas were measured for several reference minerals (anorthoclase, labradorite and augite), welded tuff and stream sediments from Snowshoe Mountain, near Creede, Colorado. Crushed and sieved tuff had an unexpectedly small variation in specific surface area over a range of size fractions. Replicate surface area measurements of the largest and smallest tuff particle size fractions examined (1−0.3mm and<0.212mm) were 2.3 ± 0.2m 2 /g for each size fraction. Reference minerals prepared in the same way as the tuff had smaller specific surface areas than that of the tuff of the same size fraction. Higher than expected tuff specific surface areas appear to be due to porous matrix. Tuff, reacted in solutions with pH values from 2 to 6, had little change in specific surface area in comparison with unreacted tuff. Tuff, reacted with solutions having high acid concentrations (0.1 M hydrochloric acid or sulfuric-hydrofluoric acid), exhibited a marked increase in specific surface area compared to unreacted tuff.

Colorado↗
USGS1994

Welded tuff porosity characterization using mercury intrusion, nitrogen and ethylene glycol monoethyl ether sorption and epifluorescence microscopy

Porosity of welded tuff from Snowshoe Mountain, Colorado, was characterized by mercury intrusion porosimetry (MIP), nitrogen sorption porosimetry, ethylene glycol monoethyl ether (EGME) gas phase sorption and epifluorescence optical microscopy. Crushed tuff of two particle-size fractions (1-0.3 mm and less than 0.212 mm), sawed sections of whole rock and crushed tuff that had been reacted with 0.1 N hydrochloric acid were examined. Average MIP pore diameter values were in the range of 0.01–0.02μm. Intrusion volume was greatest for tuff reacted with 0.1 N hydrochloric acid and least for sawed tuff. Cut rock had the smallest porosity (4.72%) and crushed tuff reacted in hydrochloric acid had the largest porosity (6.56%). Mean pore diameters from nitrogen sorption measurements were 0.0075–0.0187 μm. Nitrogen adsorption pore volumes (from 0.005 to 0.013 cm 3 /g) and porosity values (from 1.34 to 3.21%) were less than the corresponding values obtained by MIP. More than half of the total tuff pore volume was associated with pore diameters < 0.05μm. Vapor sorption of EGME demonstrated that tuff pores contain a clay-like material. Epifluorescence microscopy indicated that connected porosity is heterogeneously distributed within the tuff matix; mineral grains had little porosity. Tuff porosity may have important consequences for contaminant disposal in this host rock.

Applied Geochemistry↗
USGS1986

Authors' reply

No abstract available.

Colorado, Idaho, Montana, New Mexico, Utah, Wyomin↗
USGS1986

Use of the chloride ion in determining hydrologic-basin water budgets - A 3-year case study in the San Juan Mountains, Colorado, U.S.A.

Measurement of chloride concentration and water equivalent in precipitation and recharge at a site can be extrapolated to determine available moisture in a nearby basin. This method also may be extrapolated to a basin with similar climatic characteristics if precipitation, vegetation, and topographic data are available. The average accuracy of the total of evaporation, recharge, and runoff (assuming no storage) was about 10% of total precipitation. Soil-moisture measurements indicate the entire 10% error in moisture balance can be attributed to annual changes in storage. Data requirements for the method are considerably less than data requirements for energy-budget methods to determine available moisture. Potential applications of the method to hydrologic problem-solving are: 1. (1) Estimating total available moisture from chloride concentrations in groundwater or surface water or both. 2. (2) Modeling paleoclimate scenarios and evaluating their correctness by comparison with paleo-groundwater chloride concentrations. 3. (3) Providing an independent comparison for water budgets obtained by energy-budget methods. Obviously the method cannot be applied readily to systems with a lithologic source of chloride. Most systems primarily consisting of tuff, intrusive volcanic rock, nonmarine sediments, quartzite, and other metamorphic rocks will be suitable for application of the model.

Colorado↗
USGS1986

Late-Wisconsin paleohydrology of the West-Central Amargosa Desert, Nevada, U.S.A.

Studies of isotopes in groundwater using 14 C, 2 H (deuterium) and 18 O have provided significant insight into the paleoclimate of middle and late Wisconsin age in a typical arid environment of southern Nevada, the west-central Amargosa Desert. Evidence indicates that recharge probably was through infiltration of runoff in paleostream channels and that this runoff was important only from ∼ 17,000 to ∼ 10,000 yr. B.P. Mean annual temperature at 17,000 yr. B.P. was ∼ 8°C less than present mean annual temperature; some summer moisture was effective in recharge. Winter (October–May) temperature at ∼ 10,000 yr. B.P. was ∼ 1°C less than present; summer moisture did not contribute to recharge.

Chemical Geology: Isotope Geoscience Section↗
USGS1985

Estimates of average major ion concentrations in bulk precipitation at two high-altitude sites near the continental divide in southwestern Colorado

The composition of bulk precipitation from two high-altitude sites, established in 1971 near the Continental Divide in southwestern Colorado, has been monitored by season during the past decade. Calcium ions are the predominant cationic species; sulfate is the major anionic constituent. Bulk precipitation major ion concentrations exhibit log-normal distributions. Representative mean and standard deviation values for the major inorganic ionic species present in bulk precipitation have been calculated for three years of consecutive seasons. Standard deviations for all species, except nitrate, are similar. For two years of data grouped into quarters, deviations from mean values fall well within the plus or minus two standard deviation limit. There does not seem to be a systematic deviation from the mean concentration values, with respect to either ionic component or season.

Colorado↗
USGS1983

Sources and mechanisms of recharge for ground water in the west-central Amargosa Desert, Nevada– A geochemical interpretation

Ground water in the west-central Amargosa Desert, Nevada, was recharged primarily by overland flow of snowmelt in or near the present-day stream channels, rather than by subsurface flow from highland recharge areas to the north. Geochemical arguments, including reaction mechanisms, are used to support these findings. Carbon-, hydrogen-, and oxygen-isotope data show that much of the recharge in the area occurred during late Wisconsin time. Absence of ground-water recharge prior to late Pleistocene is considered to indicate that either climatic conditions were unfavorable for recharge or that ground-water velocities were such that they transported this earlier recharge away from the study aea. (USGS)

Nevada↗
USGS1980

Kinetic model for the short-term dissolution of a rhyolitic glass

Aqueous dissolution experiments with the vitric phase of a rhyolitic tuff were performed at 25??C and constant pH in the range 4.5-7.5. Results suggest interchange of aqueous hydrogen ions for cations situated both on the surface and within the glass. At time intervals from 24 to 900 hr., dissolution kinetics are controlled by ion transport to and from sites within the glass. Experimental data indicate that parabolic diffusion rate of a chemical species from the solid is a nonlinear function of its aqueous concentration. A numerical solution to Fick's second law is presented for diffusion of sodium, which relates it's aqueous concentration to it's concentration on glass surface, by a Freundlich adsorption isotherm. The pH influence on sodium diffusion in the model can be accounted for by use of a pH-dependent diffusion coefficient and a pH-independent adsorption isotherm. ?? 1980.

Chemical Geology↗
USGS1980

The effect of dissolution of volcanic glass on the water chemistry in a tuffaceous aquifer, Rainier Mesa, Nevada

Geochemistry of ground water associated with the Tertiary tuffs within Rainier Mesa, southern Nevada, was investigated to determine the relative importance of glass dissolution in controlling water chemistry. Water samples were obtained both from interstitial pores in core sections and from free-flowing fractures. Cation com- positions showed that calcium and magnesium decreased as a function of depth in the mesa, as sodium increased. The maximum effect occurs within alteration zones containing clinoptilolite and montmorillonite, suggesting these minerals effectively remove bivalent cations from the system. Comparisons are made between compositions of ground waters found within Rainier Mesa that apparently have not reacted with secondary minerals and compositions of waters produced by experimental dissolution of vitric and crystalline tufts which comprise the principal aquifers in the area. The two tuff phases have the same bulk chemistry but produce aqueous solutions of different chemistry. Rapid parabolic dissolution of sodium and silica from, and the retention of, potassium within the vitric phase verify previous predictions concerning water compositions associated with vitric volcanic rocks. Parabolic dissolution of the crystalline phase results in solutions high in calcium and magnesium and low in silica. Extrapolation of the parabolic dissolution mechanism for the vitric tuff to long times successfully reproduces, at com- parable pH, cation ratios existing in Rainier Mesa ground water. Comparison of mass- transfer rates of the vitric and crystalline tuffs indicates that the apparent higher glass-surface to aqueous-volume ratio associated with the vitric rocks may account for dominance of the glass reaction.

Water Supply Paper↗
USGS1970

The determination of low levels of cobalt-60 in environmental waters by liquid scintillation counting

A method for determination of cobalt-60 in waters at levels greater than 0.5 pCi per sample is presented. A modification of the method may be used to analyze fluvial sediments and soils. After the cobalt has been separated, first as the hydroxide and then as the thiocyanate complex in methyl isobutyl ketone, it is counted in a liquid scintillation system at 80% efficiency. Separation factors achieved for six isotopes are generally greater than 2,000. The time for a single analysis, exclusive of the counting and evaporation operations, is about 2 h.

Analytica Chimica Acta↗