Geologist at SAIC
- Greater Seattle Area
- Environmental Services
Geologist/GIS Analyst with SAIC’s Bothell, Washington office. I am a geologist with more than 10 years of experience in geological field investigation, analysis, reporting, and the preparation of geologic maps and reports. Have over 15 years of experience in GIS analysis and production, and have worked on projects in marine environments, highly urbanized areas, and remote areas.
Personal First Aid / CPR
- September 2010 to September 2012
Washington State Licensed Geologist
- Washington State
- License 2666
- May 2008 to May 2012
- HAZWOPR 40-HR
- April 2010
HAZWOPR 8-HR REFRESHER
- HAZWOPR 8-HR REFRESHER
- June 2010
HAZWOPR 8-HR SUPERVISOR
- HAZWOPR 8-HR SUPERVISOR
- May 2011
Skills & Expertise
- Microsoft Office
- Electron Microscopy
- Field Work
- landslide delineation
- Higher Education
- stream health/monitoring
- GIS analysis
- Environmental Science
- Remote Sensing
- Spatial Analysis
- Water Quality
- Earth Science
- Structural Geology
- Report Writing
- Technical Writing
- Water Resources
- Data Analysis
- Environmental Management
- Data Collection
- GIS applications
- Geological Mapping
- GIS software
- Data Management
FACTORS CONTRIBUTING TO LANDSLIDE ACTIVITY IN THEWINTER OF 1995-96, CLEARWATER COUNTY NEAR OROFINO, IDAHO
Authors: Aaron Wisher
- A Thesis Presented to The Graduate Faculty Central Washington University
- November 1, 1998
Significant landslide activity occurred in Clearwater County, Idaho in November 1995 and February-May 1996. Mass wasting in the study area consisted of debris slides and earthflows triggered by rain-on-snow weather events. It is important to determine what factors contribute to landsliding in this area so that reliable prediction can reduce the destruction of property. Through field observation and aerial photo analysis, the factors contributing to landslides were studied. The objectives included a study of the geology, soils, aspect, slope gradient, vegetation and slope position related to each slide. Also a goal was to assess the role of land use in triggering landslides, analyze climatic conditions during precipitation events, and to create a landslide hazard map of the Orofino, Idaho area.
Thirty-two landslides were identified in the study area. Forty-one percent of landslides were produced at sites impacted by roads, and involved either the road prism or artificial channel areas. Most of the landslides were associated with roads, and occurred at lower slope gradients than those found in forested areas. Most landslides originated on slope gradients of 30-50%. Forested slopes account for the steepest gradients, and frequently have a northerly aspect. Landslide activity occurred most frequently in soils with a basalt parent material component. The largest volume landslides occurred in forested areas in which a geologic contact between basalt and metamorphic rocks created springs. Within some areas of the study region the bedrock geology has a greater role in landsliding than land use. Historically, the Southern Oscillation has been positive in the winter months when large rain-on-snow weather events have caused flooding in the study area.
USING PETROGRAPHY, SCANNING ELECTRON MICROSCOPY, AND GIS TO EXAMINE THE CONTACT BETWEEN A SYNPLUTONIC DIKE AND ITS GRANITOID HOST
Authors: Aaron Wisher, Stewart J. Lowther, Jeffrey H. Tepper
- May 6, 2007
The sample we analyzed was collected from the contact of a ~50 cm wide synplutonic mafic dike that intrudes the Oligocene Grotto batholith, a Cascade arc intrusion located near Index, WA. Field evidence, including mutual intrusive relations, indicates that the host granodiorite was still partially molten at the time of intrusion. The dike, although finer-grained at the contact than in the center, is not aphanitic, which is also consistent with emplacement into hot host rock.
Using the SEM, 63 images of the sample were acquired at 40x magnification with a backscattered electron (BSE) detector. Using the petrographic microscope, 42 images were acquired at 40x magnification using direct digital image capture into a pc. Respective image sets were then merged and processed using Adobe Photoshop CS2. The two merged images were then put into ArcGIS to index them to each other. This allowed image distortion to be accounted for in the two datasets.
The color mosaic acquired using the petrographic microscope emphasizes crystal shape and species using polarized light. Crystal shape and size is also revealed using this method. Grayscale images acquired using backscattered electron methods show differences in atomic number and emphasize mineral areas (domains) rather than individual crystals.
Using these methods, the ability to discern changes in mineralogy across the contact from the host granodiorite into the synplutonic mafic dike were noted. Using GIS methods to “geo-reference” the two datasets gave us the ability to precisely correlate both physical characteristics and chemical characteristics in the sample. Using microbeam analysis (EDS), we measured chemical changes across zoned minerals identified using the petrographic microscope.
Authors: Aaron Wisher, Stewart J. Lowther
- October 22, 2006
The sand described in this paper comes from a low-energy beach along the shore of Puget Sound in Western Washington State. It is derived from the erosion, mainly by waves, of cliffs composed of glacial and interglacial sediments. The beach is washed by wind, waves, and tidal currents. The sand is medium gray in color and moderately sorted. Quartz grains picked from the sand are mostly angular, with sharp corners and edges, and show obvious conchoidal fractures typical of glacial processing.
The sample was prepared for the scanning electron microscope study by cementing the grains together with epoxy. The resulting epoxy block was then cut, mounted on a microscope slide, polished, and carbon coated. The grains were imaged with a backscattered electron (BSE) detector and analyzed with an x-ray (EDS) microanalizer. The mineral and chemical composition of the sample is very diverse. More than half of the grains consist of only one mineral, but the remainder are made of two or more components. Some of these polymineralic grains are obviously fragments of fine grained rocks, others are not. The most common monomineralic grains are, in order of abundance, silica, feldspars, pyroxenes, and amphiboles. Most of the silica is quartz. Some may be tridymite. Feldspars are k-spar, sanadine, and plagioclase. There is a variety of plagioclase, but most are less than AN#50. Pyroxenes and amphiboles also show a variety of compositions. The most common polymineralic grains are quartz & feldspar, pyroxene & an oxide, feldspar& amphibole, and fine-grained rock fragments. In addition to the common components, the sand contains a variety of trace minerals such as iron/titanium oxides, titanite, zircon, monazite, allenite (pentahydrite), calcite (fragments of mollusks and barnacles that inhabit the beach environment) and garnet. We conclude that the composition of this beach sand is very diverse. This diversity represents many different source rock types.
DETAILED STUDY OF THE VASHON TILL FROM THE PUGET LOWLAND, WASHINGTON, THROUGH MICROTEXTURAL ANALYSIS OF QUARTZ SAND GRAINS
Authors: Aaron Wisher, Alison Graettinger, Stewart J. Lowther
- November 7, 2004
The Vashon Till, a late Pleistocene unit, covering the greater portion of the South Central Puget Sound in Western Washington State, is a typical, moderately homogenous very poorly sorted glacial deposit. The sand fraction of the deposit is composed of lithic and feldspar fragments, and more than fifty percent quartz grains. From the fine sand portion of the sample, quartz grains were hand selected under a light microscope and mounted for study using a scanning electron microscope. Microtextures on the grains were studied to determine the assemblage of features found within the deposit, enabling comparison with other typical glacial deposits as well as those from other depositional environments. The Vashon grains display a high occurrence of sharp breakage features, with high relief, and numerous deeply incised conchoidal fractures. Along with abrasion features, these microtextures are indicative of a crushing environment, as was expected from the till. The microtextures identified within the Vashon till are fairly similar to those outlined in previous studies conducted on glacial quartz sand grains. To further outline the unique qualities of this till, comparisons were made with quartz grains found within other active environments including: desert dunes, back beach dunes, fluvial, and beach environments. As many microtextures can be formed in multiple environments, there was moderate overlap between each environment. Individual microfeatures are not independently suggestive, however, the grouping and frequency thereof provide strong evidence for the environment of deposition, and can serve as unique signature for a deposit. The data collected on the Vashon till may be useful in future attempts to distinguish between interglacial and glacial deposits within the Puget Basin, where other petrologic evidence is limited.
Authors: Aaron Wisher, Stewart J. Lowther
- Microscopy and Microanalysis
- April 5, 2002
Stewart Lowther and Aaron Wisher (2002). Application of Spatial and Feature Analysis to Electron Microscope Petrography. Microscopy and Microanalysis, 8(Suppl. 02), pp 1556-1557
Authors: Aaron Wisher, Kathy Troost L.G., Derek Booth, Michael O'neal, Scott Shimel
- November 7, 2007
Two recent mapping projects in western Washington display the benefits of new digital geologic mapping using this geologic database: 1) a regional-scale map of infiltrative soils and 2) an aquifer-susceptibility map. Runoff and consequent lack of infiltration is a major challenge for large projects seeking to mitigate increased downstream runoff into salmon-bearing streams; conversely, surface water-groundwater interactions are also of significant environmental concern because of the potential for groundwater contamination. A regional-scale map of infiltrative soils has been prepared for the planning of a major interstate freeway widening project. Substantial cost savings are realized by locating key structures near areas of infiltrative soils. The old geologic maps of the area show large, undifferentiated expanses of glacial till with low infiltration rates. The new geologic maps, based on new field work and the borehole database, reveal substantially less till and more widespread deposits with greater infiltration potential.
An aquifer susceptibility map of one of the major islands of Puget Sound has been based entirely on new geologic mapping and the geologic database supplemented with groundwater data. It replaces an older version that was developed using twenty-year old geologic mapping made with traditional methods. Queries of the database provided spatial information regarding surface and near-surface geologic materials, depth to groundwater, and whether the groundwater was confined or unconfined. ArcMap facilitated viewing LIDAR topography, aerial photography, old and new field mapping data, and cultural features to inform the geologic mapping. The new aquifer susceptibility map shows substantially more detail, and has demonstrably greater accuracy, than the old map. New mapping reveals substantially less till at the land surface than previously mapped, which translates into substantially greater aquifer susceptibility.
A MULTIFACETED APPROACH TO HIGH-RESOLUTION GEOLOGIC MAPPING OF MERCER ISLAND, NEAR SEATTLE, WASHINGTON
Authors: Aaron Wisher, Kathy Troost L.G., Bill Haneberg
- October 22, 2006
The initial geologic map was constructed by: field mapping in the winter when vegetation is at a minimum, and building a subsurface database with 2,730 boreholes, test pits, and water well logs that allows data viewing, layer searching, and cross section generation through ArcGIS©. These data were used to create a draft geologic map at 1:12,000-scale.
To enhance the geologic interpretations and to address questions in the interpretations, we analyzed (2-m cell) LIDAR data and reviewed aerial photographs. Using 3D analysis software, the LIDAR data were processed to highlight slope curvatures, slope angles, slope roughness and other abrupt elevation changes. These analyses helped to locate denuded drumlins, recessional lake deposits, paleo-shorelines, recessional outwash channels, landslide deposits and scarps, and provided geomorphic hypotheses for further field investigation. Larger drumlins and flow channels were identified that were not visible using standard topographic maps and standard LIDAR digital elevation models. Two- and three-dimensional shaded relief images with multiple sun aspects and azimuths enabled identification of mass wastage features and abundant lineaments. Although the Seattle Fault Zone crosses Mercer Island, recent fault scarps were not identified.
Interpretations from the LIDAR and aerial photographic analyses were incorporated into the draft geologic map to prepare the final geologic map. Secondary field investigations verified that the integrated interpretations are good representations of actual conditions. Without the use of LIDAR geomorphic analyses, some of the surficial deposits, of the type that would be more susceptible to ground failure during an earthquake, would have been missed during the geologic mapping. In the Pacific Northwest, earthquake risk is 2nd only to California, so geologic mapping must use all available means when feasible to best delineate susceptible deposits.
MAKING GEOLOGICAL HAZARD MAPS FROM HIGH-RESOLUTION GEOLOGICAL MAPS AND A SUBSURFACE DATABASE, MERCER ISLAND, WA
Authors: Aaron Wisher, Kathy Troost L.G., Matthew VON DER AHE, Don Cole
- May 7, 2009
The City of Mercer Island, recently updated its geological hazard maps in accordance with State regulations and the Growth Management Act. Guidance for mapping geological hazards is provided in Washington Administrative Code. “Geologically hazardous areas”, by State definition, “include areas susceptible to erosion, sliding, earthquake, or other geological events. They pose a threat to the health and safety of citizens when incompatible commercial, residential, or industrial development is sited in areas of significant hazard.” The City's suite of maps includes maps showing Seismic Hazards, Slope Hazards, and Erosion Hazards. This new set of maps represents an update of the 2002 Geologic Hazard Map Series and is based on a review of Best Available Science for the Seattle Fault and related events, a new high-resolution Geological Map of Mercer Island, a database of subsurface explorations, and depth to water data.
Comparison of the 2009 to the 2002 geological hazard maps reveals many differences and updates. The main difference between the two maps stems from the underlying geologic base map. The 2002 maps are based on a 1962, 1:63,500 scale geological map. The 2009 maps are based on a 2006 1:12,000 geological map with 4 times the level of detail of the 1962 map. The new geological map was constructed using a database of 2800 subsurface explorations and 164 exposure data points. LIDAR data were used to provide a high-resolution base for geomorphic analyses, mapping of scarps, identification of landslide deposits, and slope classifications allowing the new maps to be both more precise and more accurate. Updated 2009 maps include inventories of landslides, mapping of spring locations, depth to water data, mapping of subaqueous landslides, mapping of critical geological contacts, mapping of infiltration potential, mapping of weak deposits, and mapping of fill materials.
MAKING GEOLOGICAL HAZARD MAPS OF MERCER ISLAND, WA USING HIGH-RESOLUTION MAPS AND A SUBSURFACE DATABASE
Authors: Aaron Wisher, Kathy Troost L.G., Matthew VON DER AHE
- October 18, 2009
The City of Mercer Island, in the Puget Lowland of Washington, recently updated its geological hazard maps in accordance with State regulations and the Growth Management Act. Guidance for mapping geological hazards is provided in Washington Administrative Code 365-190-080. “Geologically hazardous areas”, by State definition, “include areas susceptible to erosion, sliding, earthquake, or other geological events. They pose a threat to the health and safety of citizens when incompatible commercial, residential, or industrial development is sited in areas of significant hazard.” The City's new suite of maps includes maps showing Seismic Hazards, Slope Hazards, and Erosion Hazards. This new set of maps represents an update of the 2002 Geologic Hazard Map Series and is based on a review of Best Available Science for the Seattle Fault and related events, a new high-resolution Geological Map of Mercer Island, a database of subsurface explorations, and depth to water data. City planners and building officials will use these maps to enforce their critical areas codes, building codes, and building permit requirements.
Comparison of the 2009 to the 2002 geological hazard maps reveals many differences. Significant differences relate to scale and base map. The 2002 maps are based on a 1962, 1:63,500-scale geological map. The 2009 maps are based on a 2006 1:12,000-scale geological map with 4 times the level of detail of the 1962 geological map. The new geological map was constructed using a database of 3054 subsurface explorations and 164 exposure data points. LIDAR data were used to provide a high-resolution base for geomorphic analyses, mapping of scarps, identification of landslide deposits, and slope classifications allowing the new maps to be both more precise and more accurate. Updated 2009 maps include inventories of landslides, mapping of spring locations, depth to water data, mapping of subaqueous landslides,...
Authors: Aaron Wisher, Stewart J. Lowther, Elizabeth BEAULIEU
- May 14, 2002
In the laboratory study of samples from a stratigraphic section of turbidites we have gained unique micropetrographic and microstratigraphic information by using the techniques of Scanning Electron Microscopy combined with those of Computer Imaging. A backscattered electron (BSE) detector produces images which clearly show the size, shape, and arrangement of the various grain components of the rocks; a microanalyzer provides whole-rock chemistry of different stratigraphic levels within the rock and the composition of individual mineral grains or parts of lithic grains; element maps show the distribution of chemical elements within the rock or within individual grains. Computer processing greatly improves the quality of the original images, allows enlargement of these images to enhance details, and allows us to assemble several individual images into one continuous image. The latter technique is especially useful in examining the detailed characteristics of a whole graded bed, the relationships between a single bed and the beds above and below it, or a sequence of several beds.
The samples used for the analyses are polished petrographic thin-sections or thick-sections cut perpendicular to the stratification. The BSE images are captured on film and digitized with a film scanner, or are taken directly into the computer with an A/D converter. We use Adobe Photoshop to process the images but there are many other software packages which work very well. There are also several program, including Photoshop, which can be used to assemble (stitch) adjoining frames into large mosaics or strips. Analysis of processed images can be carried out with software which produces gray-level histograms, "particle analysis" or techniques of stereology.
QUENCH TEXTURES, LITHIFICATION, AND MODES OF CRYSTALLIZATION IN A COOLED SLAG BLOCK FROM A SMELTER AT NORTHPORT, NORTHEASTERN WASHINGTON STATE
Authors: Aaron Wisher, Stewart J. Lowther
- October 30, 2007
This investigation examines a block of slag approximately 35 cm square dumped out molten after passing through the smelting process to extract lead and zinc. It has cooled and solidified from the outside into the middle, and in that respect is analogous to a lava pillow – the edge cools very quickly and the deeper into the block the slower was the cooling. Most of the block is crystalline and scattered through it are small grains of sulfide minerals, some of which are Pyrite, some Chalcopyrite, a few consist of both minerals. And at least one grain included native copper and native silver. We have made the analyses of the rock based on a sequence of polished sections cut perpendicular to the surface and extending into the center. These sections were analyzed using a scanning electron microscope (SEM) which produced a series of backscattered electron (BSE) images and energy-dispersive (EDS) microanalyses. The outermost part of the rock consists of glass with a uniform texture and composition (predominately O, Fe, Si, Ca, Al, K, and Mg). Below the homogeneous glass zone the glass has separated into two main phases which differ in the Ca/Fe ratio. Further down these phases begin to form distinct crystal domains, one of which is coarser than the other. The larger domains have a larger Ca content and a more uniform overall composition. The smaller domains have a higher Fe composition and a more variable composition. Towards the center of the block the crystals become larger and the compositions more uniform, although the high Ca (lower Z) domains are still coarser than the high Fe (higher Z) ones. Also, the low-Z crystals are aggregated into large obvious pinnate leaf-like structures. Microanalysis indicates the coarser lower-Z crystals are basically calcium-iron-magnesium-aluminum silicates and the higher-Z crystals are iron-calcium-magnesium silicates.
Authors: Aaron Wisher, Kathy Troost L.G.
- October 30, 2007
Groundwater withdrawal from thick peat deposits has caused damaging settlement in overlying and nearby structures in the Greenwood bog of Seattle. Bogs and glacial recessional lake deposits frequently contain compressible deposits of peat and organic-rich silt. These deposits are present in relatively isolated but widespread and buried locations throughout the City of Seattle. Most of these bogs began growing at the close of the last glacial period but are now covered by fill, in some cases 18.3 m (60 ft) thick.
Peat deposits are easily found using a simple query of a geotechnical database containing subsurface layer data from over 35,000 boreholes. Using borehole data, 63 deposits were mapped in Seattle and 5 types of former bogs are recognized based on their formation: 1) those formed at the heads of or along modern streams, 2) those formed at the heads of or along recessional streams, 3) those formed in apparently isolated upland depressions, probably kettles 4) those formed in the Duwamish Valley floodplain and marine estuaries, and 5) those formed adjacent to Lake WA and related to the artificial lowering of the lake in 1916. The thickest [18.3 m (60 ft)] and most continuous peat deposits occur adjacent to Lake Washington. However, saturated continuous peat deposits on the order of 4.6 m (15 ft) thick are present in all types. Most peat deposits are generally 0.6 to 2.4 m (2 to 8 ft) thick. Type 4 deposits are the least continuous and tend to be the thinnest of the 5 types.
Peat occurs in bogs and as discontinuous lenses in lacustrine and fluvial deposits, in the latter case, mapping discrete peat lenses is not plausible. For these deposits with discontinuous lenses of peat, maps show boreholes where peat was encountered and conversely where peat was not encountered. Where peat occurs in lacustrine deposits, soft, thick, organic-rich silt is often present.
Iron and titanium oxides in the rocks of Mt. Rainier volcano, Washington State
Authors: Aaron Wisher, Stewart Lowther
- June 4, 1996
Lowther, J. S.; Wisher, Aaron P., 1996, Iron and titanium oxides in
the rocks of Mt. Rainier volcano, Washington State [abstract]:
Geological Society of America Abstracts with Programs, v. 28, no.
5, p. 86.
Scanning electron microscopy of a stratigraphic section of rocks from Mt. Rainier volcano, Washington State
Authors: Aaron Wisher, Stewart Lowther
- July 11, 1996
Wisher, Aaron P.; Lowther, J. S., 1996, Scanning electron
microscopy of a stratigraphic section of rocks from Mt. Rainier
volcano, Washington State [abstract]: Geological Society of America
Authors: Aaron Wisher, Kathy Troost L.G., Scott Shimel, Derek Booth
- U. S. Geological Survey Open file report 2005-1252
- February 13, 2005
Troost, K.G., Booth, D.B., Wisher, A.P., and Shimel, S.A., 2005. The geologic map of Seattle - U. S. Geological Survey Open file report 2005-1252, scale 1:24,000.
English(Native or bilingual proficiency)
Central Washington University
1996 – 1998
University of Puget Sound
1992 – 1996