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Minerals, Petroleum, Geothermal Resources, Seismic Hazards, Landslide Hazards, Tsunami Hazards, and Groundwater Flow


The science of geology encompasses the study of the structures and materials of the earth such as faults, folds, tectonic plates, rocks, sediments and minerals as well as the qualities and movement of subsurface fluids, both liquids and gases such as WATER, CRUDE OIL, MAGMA, NATURAL GAS and poisonous gases. The modern science of geology was born in England in the late 18th century in the form of the deductions of Dr. James Hutton as a result of his work in agriculture and his observation relating to understanding the concept of geologic strata (layering). His work was instrumental in solving problems associated with the construction of canals and permitted the proliferation of canal building and their economic benefits in the early 19th century. Hutton, a Scottish physician, chemist and businessman, developed a theory regarding the cyclical evolution of landforms, rock layers and sediments, mountain building and erosion. His theories were presented in this age of 'gentleman scientists' before the Royal Society in 1785.

This simplified slice or 'cross-section' illustrates the geometry of groundwater flow in porous sediments or geologic strata (aquifers) either unconfined or confined by low-porosity strata (aquitards or aquicludes). USGS


In the field of ENVIRONMENTAL SCIENCE we and our clients are concerned with the extent, identities and concentrations of man-made contaminants in soils, sediments, porous rock layers, surface waters and groundwater. The nature of their movement is governed to a great extent by the three-dimensional geometry of the impermeable aquifer boundaries and the porous aquifer materials through which they travel. Since most cities and industries are located on the relatively flat plains of valleys or coasts, much of our work deals with the groundwater which in these areas is generally located within soft sediment layers deposited by rivers, lakes, glaciers, volcanic flows or landslides on valley floors and coastal plains, or occasionally within the much older underlying hard rock layers or bodies.

Niagara Springs in Idaho issues from the talus (boulder) field beneath a steep basaltic bluff above the Snake River Valley. The basalt here is a 395,000 yr old volcanic flow, one of many which occupy the Snake River Valley where the great river recedes from its icy origins in the Grand Tetons of Wyoming before finding its way to the Columbia River, Washington, Oregon and the Pacific Ocean. It is certainly true that all rivers flow into the sea (exceptions are isolated basins such as the Great Salt Lake and the Dead Sea) but equally true that all mountain rainfall ultimately rises from the sea. This cyclical exchange is known as the water cycle or 'hydrologic cycle.' Image credit: fishandgame.idaho.gov

Expanded content CONTINUED below ...

Charges Filed: Fatality at a UCLA Research Lab

9 JAN 2012: This recent case revealing an apparent failure of safety precautions illustrates both the potential for tragedy with regard to loss of human life and the potential for high litigation costs. In this case, a young woman died of burns sustained ... More: [NEWS]

USEPA: Ruling: EPA Must Implement Controls to Ensure Proper Investigations

9 JAN 2012: Grantees awarded EPA Brownfields Assessment Grants must meet AAI ("All Appropriate Inquiry") requirements. AAI is the process of evaluating a property for potential environmental contamination ... More: [LAW]

Mold - A Significant Biological Hazard

1 FEB 2012: According to public health expert, Dr. Joseph Jarvis: "While it may not be possible to determine the level of exposure needed to cause a problem, there is much documentation that exposure to indoor mold can cause respiratory allergies ..." More: [EDUCATION]

Construction Accident Investigation Files

9 JAN 2012: FEATURED REPORT: A new example from our Constuction Accident Report Files will be available for your review here. ... More: [CONSTRUCTION]

. Expanded Content. . Continued from left column.


The locations and nature of these large scale, mountains, valleys and coastal plains are in turn governed and understood in part by a newer geologic theory known as plate tectonics. The very existence of mountains, valleys, continents and oceans are either directly or indirectly explained by the same tectonic theory. Since the middle of the 20th century, when acoustic and magnetic mapping of the ocean floors confirmed this unifying theory of geology, we have understood that the surface or solid crust of the Earth is not unlike the shell of an egg and is heavily fragmented.

This USGS preliminary map excerpt reveals the locations of major active (Quaternary) fault zones such as the Denali (B) and the Totschunda (D), as well as many less well known faults. As in the case of the Olympic Mts. in Washington state, these faults often mark the margins of 'accretionary terrain, crustal material which in this case is fused to the margin of the American continent by the motion of the Pacific Plate.

It is comprised of numerous large PLATES, 5 to 25 miles thick, riding slowly atop a deeper and partially melted mantle. When these plates collide or move relative to one another, we find a concentration of earthquake activity, landslides, tsunami, volcanic activity and mountain building.

| Recent Earthquakes - USGS Realtime Global Map |
| Recent Earthquakes - USGS Realtime USA Map |

These plate motions occur at an extremely slow pace, a matter of a few centimeters or inches per year at most. But over periods of thousands of millennia, they move many tens of miles. And because these mountainous areas tend to be both beautiful and rich in natural resources and deep harbors, population centers tend to develop within them. The primary states served by Aerotech - Alaska, Washington, Oregon, Idaho and California - are among those whose landforms, geologic hazards, and in turn hydrogeology (the quality and behavior of groundwater) are impacted to some degree by their proximity to the tectonic plate boundary which lies along the western margin of North America.

The relatively small Juan de Fuca Plate can be seen beside Washington and Oregon. Though small, the energy released by earthquakes and eruptions caused by minute slippage along its trace can cause damage rivaling that commonly linked to the San Andreas. USGS

OCEANS : Heavy dark basaltic rock dominates the thin oceanic plates which tend to form ocean floors while less dense granitic rock types dominate the thicker continental crusts. Because the interior of the earth contains much radioactive material which generates great heat, the middle magmatic mantle between the Earth's metallic core and the thin cool crustal plates on which we live, convects (circulates). In places around the globe where heat and magma rise, we see great submarine fractures surrounded by great arcing submarine mountain chains where the oceanic plates are split and forced apart, with new crust forming linear bands. Iceland is among the very few places on Earth where one of these great crustal fractures can be seen on dry land. Along with the hazards of the associated volcanic eruptions, the benefits of geothermal energy are found in these places. The Dead Sea and the East African rift are relatively new rift zones likely to become oceans in the distant geologic future, just as the Atlantic Ocean first formed when Europe and Africa began to separate from the Americas millions of years ago.

MOUNTAIN RANGES : The Aleutian Islands of Alaska and the Island of Japan have formed as a result of rising magma derived from the melting of the Pacific tectonic plate 'diving' or descending underneath the less dense North American Plate or micro-plates adjacent to the Eurasian Plate. Other Alaskan mountain complexes, much like the Himalayan Mts. or the Ural Mts. represent areas where crustal material has been fused to a continental plate after a collision event. The volcanically active Cascade Range - including Mt. St. Helens - has actually formed due to the melting of a micro-plate known as the Juan de Fuca Plate. The volcanic activity on the peninsula of Italy and Greece is also caused by the same process. The African Plate is descending beneath southern Europe, and the Alps, not unlike the Olympic Mountains of Washington state, bear evidence of major faults where 'slivers' of the descending plate have been thrust up, deformed and fused to the continental plate. A third type of tectonic plate boundary known as a 'strike-slip' fault is seen in the form of the well-known San Andreas Fault Zone, running like a crustal zipper from the Baja Peninsula to Pacifica, California. As many are aware, the Baja Peninsula, Los Angeles and San Francisco, attached to the Pacific Plate, are slowly but surely being transported northward toward points offshore of the Oregon coast. The great San Francisco quake of 1906 is an example of the destructive power of waves generated on the land surface by movement on major faults such as the San Andreas. The Alaska quake of 1964 is another example where destruction was greatly increased by the generation of tsunami waves caused by vertical seafloor displacement.

Video footage: | Alaskan Earthquake of 1964 |

At Mag. 9.2 the 1964 quake remains the largest quake recorded in North America. USGS Earthquake data:
| USGS Report - Valdez, Alaska Earthquake |

Land masses north of the fault were uplifted as much as 50 feet while subsidence south of the fault approached 10 feet. Remarkably, a 67 foot tsunami wave and the catastrophic drainage of the Valdez Harbor prior to the occurrence of the wave were filmed by a sailor aboard a cargo vessel at the old Valdez docks. He had been filming young people on the docks who had come to see the large ship. None present on the dock survived. The wave at Valdez rose as high as 170 feet along the hillsides adjacent to the Prince William Sound.


California's Sierra Nevada Range was once an active volcanic arc 'venting' magma plumes rising from a subducting plate, just as the` volcanoes of Cascadia are an active example of the 'venting' of melted oceanic crust riding underneath the lighter and thicker continental crust. A second class of volcanoes is seen in that line of extinct volcanoes we know as the Hawaiian Islands, with the newer and most active volcano at its eastern end in the form of the 'Big Island' of Hawaii. Many are unaware that Yellowstone Park is dominated by an enormous active 'super-caldera' which, like the 'Big Island' marks the terminus of a line of extinct volcanoes and caldera, extending here to the southwest toward northern Nevada. These linear trails of extinct volcanoes offer further evidence for the Tectonic Theory, of existence of moving crustal plates riding over mantle 'hot-spots.' Yellowstone's geothermal activity, seen in the form of geysers such as 'Old Faithful', not entirely unlike that in Iceland's rift zone, is linked to the presence of these underlying magma plumes and the heat they generate above. Unlike Iceland which is situated atop a plate boundary, Hawaii and Yellowstone are examples of isolated hot spots. The origins and causes of these upper mantle hot spots so far from the margins of large tectonic plates remains a bit of a mystery.

Geologists investigating the devastated terrain are dwarfed by these enormous Douglas Fir trunks, toppled in an instant over an area of many square miles by the blast and 'pyroclastic' (hot ash / debris) flow issued by Mt. St. Helens after the May 1980 eruption. In turn, the trees are dwarfed by the nearby hillside and the remnants of the volcano dwarf the hillside. Photo credit: Lynn Topinka 24 Sep 1980

MAJOR FAULTS : There are numerous major and minor faults and complex fault zones directly or indirectly linked to the forces and energy of plate tectonic margins. For example, if we think of the crust of the earth as behaving much like fractured shelf ice where sometimes we see horizontal compression and at other times extension, we might better understand the Rocky Mountains. The high plateaus of the Colorado Rockies are characterized by many major faults marking the edges of rising blocks of crust with the Yellowstone hot spot to the north. The Grand Canyon was formed by millions of years of erosion where the Colorado River has carved its path into the vast rising plateau. But between this plateau and the Sierra Nevada Range, the desert areas of western Utah, Nevada, and southern California are characterized by crustal extension where roughly rectangular mountain blocks are separated by fallen valley blocks usually a few tens of miles wide and a hundred or so miles long. This large scale tectonic structural region, known as the 'Basin and Range,' is not unlike the fields of small-scale ice crevasses we see near the ends of glaciers or on shelf ice where the margins are melting and pulling laterally on the ice further inland.

This USGS block diagram illustrates the basic geometry of the 'normal' faults which commonly mark the margins of the numerous mountain ranges of the 'Basin and Range' province, and many other mountainous area.



A third class of geologic features is caused by the opposite of the 'extension' or pulling apart of the Earth's crust, compression of the crust. This also occurs near or some distance inland of a subducting oceanic plate margin. The Olympic Mountains of Washington are an example of this, where former oceanic crust has been thrust up and over the existing continental margin. We see the same sort of mountainous slivers of continental crust thrust eastward in the mountains north of Salt Lake City through western Montana, Idaho and into the eastern Canadian Rockies.

In this USGS graphic we see many of the relatively recent (Quaternary) faults and the distinct tectonic block pattern of the 'Basin and Range' province.

Ancient rock layers (strata, aka 'formations') are often deformed and folded in these regions much as a compressed rug on a hardwood floor is folded into ripple-like ridges and depressions. This sort of geologic structure can create spaces where natural gas or petroleum accumulate if petroleum 'source rocks' are located nearby. The Labrea Tar Pits of Los Angeles are an rare example of one such area which happens to leak at the surface by way of a fault penetrating the deeper porous oil-bearing rocks below. More commonly considerable exploration, drilling and engineering is necessary to access and remove crude oil from relatively deep reservoirs. The north slopes of Alaska and the Gulf of Mexico, the Niger Delta and the North Sea are examples of petroleum reservoirs located in porous pockets created by tectonic extension - the same extension that created the Gulf basin itself. The oil reservoirs found in the Middle East tend to be those formed by porous traps created in areas of tectonic compression.

In geologic zones such as the East Pacific 'Cordillera' (series of moutain chains) where new continental crust is being added by horizontal thrust faulting, we often find a complex mixture of juxtaposed features, some much older and far more deformed, faulted and folded, mixed with massive blocks of exposed deep magma bodies called plutons and ancient lava flows derived from old inactive volcanoes and modern active volcanoes such as Mt. St Helens in Washington and the Redoubt Volcano in Alaska.


Glaciers, often hundreds or many thousands of feet thick, deposit complex mixtures of clays, silts, sands and gravels beneath and beside the ice flows. Related debris ridges and river deposits as well as glacial lakes can form at their extreme margins. In North America the most recent period of widespread continental glacial advance came to an end about 14,000 years ago. The Puget Lowlands of Washington State are among those areas whose near surface topography, shallow geology and ground water conditions are determined to a great extent by glaciers and glacial sediment deposition. Glaciers persist at higher elevations today, even on mountains such as Kilimanjaro at the equator. The residents of Alaska, the Pacific Northwest, California, as well as the Alps are no stranger to these modern glaciers or to the narrow steep walled valleys such as Yosemite which were carved by knife-like glacial movement during the cold glacial periods.

Glacial sediments are generally relatively young and have not yet been 'lithified' (transformed into rock by high pressures or temperatures). While distinct rock layers and masses with distinct composition can extend consistently over many miles or hundreds of miles, both the vertical and horizontal variation in glacial sediment type, from gravel, sand, silt to clay and mixtures of all of these, can vary abruptly on relatively small scales of as little as several tens of feet. Though most geologic units are deposited and lithified over vast periods of time, we sometimes find evidence of brief instances of catastrophic flooding due to the erosion or collapse of glacially-formed dams where both massive erosion and sediment deposition results. The enormous ridges, deep gorges and pothole features of the 'Scablands' of central Washington are an example of the results of one of these great floods.

Canyons and valleys which have not been created by or 'excavated' by glacial forces (for example, those created by tectonic activity and or erosion by water) are commonly gradually filled with river (fluvial) deposits, by lake (lacustrine) deposits, or by landslide deposits. In many areas in the western United States and Alaska we also find alluvial fan deposits. These are broad cone-shaped fluvial deposits which 'fan' out where a river leaves the confined space of a canyon and enters a more broad valley or coastal plane. For example, U.S. Route 15 in Utah between Salt Lake City and Las Vegas rides atop a series of alluvial fan deposits, winding around and over them.

Consideration of all of these factors, and the sometimes complex 3-dimensional subsurface geologic geometry created as a result of the interplay of these forces, play a role in the study of the extent of environmental contamination in soils and groundwater as well as the estimation of future contaminant migration under the ground and in some cases into surface water bodies such as rivers and lakes.

Principle Aquifers of Washington and Oregon - USGS: Yellow represents unconsolidated basin sediments. Dark reds represent basaltic rock aquifers, light red mark volcanic and sedimentary rock aquifers, and gray marks older rock aquifers yielding relatively little water.


While geologic maps provide considerable insight into the nature of the geologic materials, structures and faults beneath our feet, Phase I and Phase II investigations may require the examination of existing soil boring logs and monitoring well data or the advancement of new soil borings and the construction of monitoring wells on a subject property in order to define detail at the scale of the property or contaminant plume. These data and laboratory analysis of soils or ground water acquired in these field operations permit us to determine with considerable precision the nature of the geologic units beneath or near the property, the depth of various geologic units, the depth of the groundwater table, the direction of groundwater flow, and the amount and type of chemical contamination present at the site. Other less invasive exploratory methods such as ground penetrating radar and electrical resistivity surveys may also reveal the details of geologic structures and the extent of the contaminant 'plume' at or near the subject property in the areas between and beyond soil borings and wells. Seismic surveys - employing the artificial generation of vibration in the ground - can also be utilized to 'see' the geologic strata and structures.


Once contamination has been discovered and its nature and extent have been defined in soils or groundwater, two basic methods are employed to remove or minimize the presence of contaminant. First, the source of contamination is repaired or removed. Simple excavation of near surface soils beside and beneath the source of the contamination (for example, underground storage tanks or surface spills) is often the next step. Where contamination has entered a groundwater aquifer beneath the contamination source, groundwater must be monitored and may require remediation to prevent further migration of the contaminant plume. The surface discharge point for groundwater may be a nearby well, a river, a lake or an ocean at some considerable distance from the source of contamination. Although there may be several linked or unconnected aquifers beneath a site, contamination is most commonly found within the uppermost water-bearing geologic unit. Once the extent of the contaminant plume is determined and the source has been neutralized or removed to prevent further release of contaminant, if necessary contaminated ground water can be pumped from the ground and treated on site or disposed of off-site. In some cases, soil gas ventilation systems may also be installed in order to remove hazardous vapors which can accumulate in porous geologic zones above the groundwater table where groundwater or soil contamination is present below.

Our goal at Aerotech Environmental Consulting is to define and then eliminate your environmental problem in the most efficient manner available to permit your site to be designated by the regulating agency as requiring 'No Further Action' in accordance with pertinent local, state and federal regulations.

McDermott - Aerotech staff - Feb 2012

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