Geologic Time Scale The Geologic Time Scale is an international system used by geologists to classify and identify major geologic events and formations. The geologic timescale essentially categories the earth’s entire geologic (and biologic) history, within a series of defined eons, eras, periods, epochs, and ages. Updates & Maintenance The geologic time scale is continuously…
Plutonic Rock (Igneous) Definition The term “Plutonic” in the field of geology refers to an igneous rock, wherein the magma had originally cooled, solidified, and crystalized underground. A plutonic rock is generally coarsely crystalline (phaneritic) and is formed during a massive geologic intrusion of magma. In fact, outcropping (or daylighting) plutonic rocks are geologic features…
Tsunami Tsunami: In the seismology branch of geology, a tsunami is an oceanic wave (gravitational) that is produced by seismic activity on the ocean floor. Common triggers of tsunamis are large-scale short duration earthquakes, volcanic eruptions, or other submarine earth movements such as subsidence and slope failure.
Sand Boil A “Sand Boil” is a cone-shaped deposit of sand that is formed during an earthquake. A Sand Boil occurs when subsurface sand layers liquefy and are then blown to the surface through cracks.
Seismic Moment Seismic Moment: In the seismology branch of geology, seismic moment represents a measure of the size of an earthquake, depending on the area of rupture, the rigidity of the rock, and the amount of slip from faulting.
Moment Magnitude (M) Moment Magnitude (M): In the seismology branch of geology, moment magnitude is the magnitude of an earthquake that scientists estimate by using the Seismic Moment.
Subsidence “Subsidence” is a geologic condition, in which a localized mass movement occurs, resulting in the downward settlement of the earth over time. When subsidence occurs, the actual ground surface elevation is lower. This occurrence of the ground surface sinking is typically caused by groundwater table and aquifer reductions, by which the soils become more…
Surface-Wave Magnitude “Surface-Wave Magnitude” is the magnitude of an earthquake that scientists estimate using measurements of the amplitude of surface waves.
Topple Definition Topple – Slope movement due to forces that cause an overturning moment about a pivot point below the center of gravity of the unit.
Runoff (R) The term “Runoff” (R) in hydrogeology and geology refers to the part of rainfall which accumulates on the ground surface and naturally forms into flowing streams.
Potentiometric Surface The term “Potentiometric Surface” means the hydrogeological surface that represents the total hydraulic head of groundwater from a confined aquifer or semi-confined aquifer that’s under pressure. The Potentiometric Surface of an aquifer is defined by the level to which water will rise in a groundwater monitoring well (that’s exclusively screened within said aquifer).
Permeability “Permeability” in engineering geology and geotechnical engineering refers to the property of a soil sample (or porous rock) which relates to transmitting a fluid within. Permeability measures the relative case of flow under unequal pressure. Permeability is calculated using Darcy’s Law.
What is an ALTA Survey? An ALTA Survey is a specialized Boundary Survey of a property that adheres to strict standards developed by the American Land Title Association (ALTA) and the National Society of Professional Surveyors (NSPS). An essential part of any legal ownership of land, the boundaries of a property must be properly and…
Hydraulic Conductivity (K) “Hydraulic Conductivity” (K), in hydrogeology and hydrology, represents the capacity of a porous medium (such as soil) to transmit water, as per Darcy’s Law. To illustrate, the rate at which fluid can move through a permeable medium (such as soil), depends on the properties of that soil (such as intrinsic permeability) and…
Porosity (n) “Porosity” (n), in the geological engineering field, is a percentage value that represents the bulk volume of a rock or soil, that is occupied by the void space within. Porosity (n) Formula Porosity (n) = [(Volume of Voids ÷ Total Volume) x 100%]
Reformation of Factory Farming The global population as of July 2020 is 7.7 billion, according to the United States Census Bureau. And the United Nations has estimated that this number will grow to 10 billion by 2050. If the human population does continue to grow so rapidly, an increase in the amount of available food…
What is a Vapor Barrier Membrane for Soil Gas Mitigation? A vapor barrier, or a sub-slab vapor membrane, is a layer of protective material that prevents toxic vapor intrusion into buildings. An impervious vapor barrier can be a combination of plastic film, fabric, and sheets. And there are also roll-on and spray-on applications. Contractors usually install…
Licensed Professional Geologist A “Licensed Professional Geologist” or a “Certified Professional Geologist” is a person who is certified by a State and/or Federal agency (such as the California Department of Consumer Affairs, Board for Professional Engineers, Geologists & Land Surveyors), and has proven be educated, formally trained and professionally competent per government standards, to practice…
Consistency The term “Consistency” in the fields of engineering geology and geotechnical engineering means the degree of adhesion between soil particles within a sample, that are observed to resist deformation or rupture.
Consolidation “Consolidation” in geology refers to the gradual or slow reduction in the volume of a soil sample (representing a larger soil mass), and the increase in density in response to an applied increasing load, or compressive stress.
Critical Void Ratio The “Critical Void Ratio,” in soil science and geology, represents the final void ratio of a soil sample, at ultimate strength. And Critical Void Ratio is achieved by the loose and dense samples of the same soil post-shearing.
Degree of Saturation (SR) “Degree of Saturation” (SR) is an engineering geology term and refers to the ratio of the volume of water to the total volume of void space. The Degree of Saturation or SR-value ranges from 0% to 100% (0% being completely dry, and 100% being fully saturated). Degree of Saturation Formula Degree…
Direct Shear Test A Direct Shear Test is a geotechnical engineering laboratory procedure that measures the shear strength value of a soil sample.
Dilatancy “Dilatancy” is the increase in the bulk volume of a soil substance during deformation. Dilatancy is caused by the change from a close-pack structure to an open-pack structure.
Gap-Graded The term “Gap-Graded” is used by geologists, engineers, and soil scientists in the geotechnical engineering field to describe the gradation of a soil sample, specifically when some particle sizes are missing. Aside from being “gap graded,” a soil sample can be described as “well-graded” (also referred to as poorly sorted), or “poorly graded” (or…
Adsorption “Adsorption” in geology, refers to the attraction and adhesion of the ions or molecules of a solution, onto the surface of a solid.
Effective Size (D10) “Effective Size” (D10) is an engineering geology term. Effective Size represents a diameter that directly corresponds to the percentage, by weight, of grains that equal to 10% on the grain-size diagram. To illustrate, 10% of the soil sample particles are finer-grained, and 90% of the sample particles are coarser than the “effective…
Effective Stress (σ’) “Effective Stress” (σ’) is a geotechnical engineering term. Effective Stress is a function of “total stress,” and is due to the solid particles of soil. Effective stress represents an excess of stress above pore-water pressure (or neutral stress). Effective Stress Formula Effective Stress = Total Stress – Pore-Water Pressure.
Liquefaction Liquefaction: Liquefaction is the process by which there is: (1) a sudden and significant decrease of shear resistance in a soil sample (cohesion-less); (2) a sudden (but temporary) increase of the pore-water pressure of a substance; and (3) a solid mass of soil that is transformed into a fluid state mass. In the event…
Liquid Limit (LL) “Liquid Limit (LL)” in the field of geological engineering, refers to the upper limit of the “plastic state.” This is a separation of the plastic phase and viscous liquid phase when measuring soil consistency. Mathematically, it is the water content (basing on the percent of dry weight), at which two sections of…
Hooke’s Law “Hooke’s Law” is a geological statement relating to the elastic deformation of rocks. Hooke’s Law states the strain of an earth-material is linearly proportional to the applied stress.
Dry Density (ρd) “Dry Density” (ρd) is a value that represents the density of soil when it is completely dry. To illustrate, it equates to (“bulk density” / 1) + “water content.” This is a common geotechnical engineering laboratory procedure. Dry Density Formula Dry Density = [(Bulk Density ÷ 1) + (Water Content)]
Dry Strength “Dry Strength” is a value that represents the strength of a soil sample, when dry, as determined by the crushing test. There is a common geotechnical engineering laboratory procedure for determining the cohesiveness or plasticity of a sample with organic or inorganic clays and silts.
Hardpan (Caliche) “Hardpan” is a highly dense and solid layer of soil near the ground surface, which is usually comprised of clay or silty-clay soils. Hardpan forms by cementation over time, during the process of precipitation of insoluble substances such as calcium carbonates, silica, iron oxides, and other organic matter. “Hardpan” is a term mostly…
Soil pH Test Strips The pH of soil can be measured using a variety of different devices, or pH testers, which can quickly indicate to a user the pH of their soil. Soil ph test strips determine a numerical value indicating the acidity or alkalinity of soil. The pH scale ranges from 0 to 14,…
Disposing of Hazardous Waste & Household Waste It is common knowledge that certain items, like batteries, for example, should not be disposed of in the trash for general waste pick-up. And depending on where you live, it might be illegal to dispose of such items in this way. Fortunately, no matter where you live, every…
Bowser Underground Gasoline Storage Tank & Storage Outfit Sylvanus Freelove (S.F.) Bowser is credited with inventing the first gasoline pump and storage tank combination in 1885. Originally, he invented the pump to dispense kerosene, but as the popularity of gasoline increased with the rise of the automobile, so too did the application of the Bowser…
Blue Opal Gemstone The blue opal gemstone, like all other types of opal, is not a mineral. Instead, it is an amorphous mineraloid, which means it is a substance that comprises a specific arrangement of smaller microcrystalline silicas, which result in a blue spectrum of light reflection. Blue opal has an appealing luster and appearance,…
Human Health Risk Assessment (HHRA) A Human Health Risk Assessment (HHRA) evaluates the potential dangers to people where there may be some exposure to chemical contaminants in soil, groundwater, ambient air, or soil gas. Typically, the recommendation for an HHRA stems from the Phase 1 Environmental Site Assessment process. However, the awareness for indoor air…
Indoor Air Quality Testing Indoor air quality testing involves collecting and containing samples of ambient air from inside a building and analyzing them to determine what chemicals may be affecting human health and safety. Sources of pollution may exist on- or off-site and can accumulate above- or below-ground. Indoor air quality testing is necessary at…
Fire Opal Gemstone – Geology & Mineralogy Information Fire Opal is an amorphous mineraloid comprising an accumulation of tiny hydrated silica spheres that produce a dominant reddish-orange spectrum upon light reflection. Although it is commonly misclassified as a “mineral,” fire opal is actually not a mineral because it does not have its own crystalline structure….
Environmental Law Environmental Law refers to the various categories of law that are put in place to protect the quality and condition of the earth and the environment. This sect of law aims to protect the well being of people and to preserve the earth’s natural resources, reserves, and wildlife. In fact, environmental laws apply…
Retaining Wall Retaining Wall: A structure that provides the support needed to hold (in place) a mass of earth, preventing it from moving downhill. Retaining walls are relatively rigid structures comprising footings and a drainage system, in order to retain the soils between two different elevations. Updated May 25, 2020. Construction & Design A lot…
San Carlos Olivine & Peridot The San Carlos Apache Reservation is one of the earth’s richest resources olivine-rich rocks. San Carlos Olivine is a name that refers to a group of closely related minerals, with very similar chemical compositions, that are found in igneous rocks in the Apache Reservation. These olivine minerals consist of silicon…
Phase 2 Environmental Recommendation In some cases, there may be a Phase 2 Environmental recommendation for a property, resulting from a Phase 1 Environmental Site Assessment. Typically, this occurs when one or more Recognizable Environmental Conditions indicate the possibility of subsurface contamination. For instance, a property with an in-place underground storage tank (UST) can likely…
Methane Barrier for Soil Vapor Membrane A methane barrier is an impervious soil vapor membrane underlying building slabs and retaining walls. And it has the purpose of stopping subsurface methane soil gas from intruding inside structures. The overall goal is to protect the human occupants of buildings overlying methane soil gas pockets. For instance, petroleum…
10 Things to Know Before Methane Barrier Installation Methane barrier installation is part of the overall methane mitigation construction process. Methane barrier construction in Los Angeles requires the use of specific materials with LADBS approval. Additionally, the applicator must have the proper certifications from the local building department and impervious vapor membrane manufacturers. In fact,…
Remedial Action Plan A Remedial Action Plan, or Remediation Plan is a guideline that proposes a series of engineering and geological procedures, in order to feasibly perform contamination cleanup actions over a strategic period of time. When pollution exists on a property, at levels requiring cleanup, it is important to design the most appropriate course…
Understanding the Underground Storage Tank Abandonment Process The underground storage tank abandonment process is a complex series of construction and demolition tasks that require intensive environmental regulation and oversight. An underground storage tank, or “UST,” is a large vessel, usually comprising steel or fiberglass, that serves to hold large volumes of liquid. These tanks typically…
Remediation after Phase 2 Environmental Site Assessment Contamination Remediation refers to the process of cleaning up a property with contamination issues that are usually discovered during the Phase 1 Environmental Site Assessment (ESA) and Phase 2 Subsurface Investigation process. Today, there are a variety of remediation methods and technologies to apply at a site. And…
