SCIENCE EDUCATION > Environmental Sciences

Earth Science

This collection features topics ranging from geology to geochemistry; with a variety of demonstrations including physical and chemical properties of minerals and the analysis of rock formations.

  • Earth Science

    05:35
    Determining Spatial Orientation of Rock Layers with the Brunton Compass

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    Most rock units exhibit some form of planar surfaces or linear features. Examples include bedding-, fault-, fracture-, and joint-surfaces, and various forms of foliation and mineral alignment. The spatial orientation of these features form the critical raw data used to constrain models addressing the origin and subsequent deformation of rock units.

    Although now over 100 years since its invention and introduction, the Brunton compass (Figure 1) remains a central tool in the modern geologist’s arsenal of field equipment. It is still the primary tool used to generate field data regarding the geometric orientation of planar rock surfaces or linear rock features. These orientation measurements are referred to as strike and dip, and provide the fundamental data for making geologic maps. Furthermore, the Brunton Compass can also function as a traditional compass for location exercises and triangulation. Finally, it can also serve as a pocket transit for measuring angular elevations. Figure 1. The Brunton compass.

  • Earth Science

    07:12
    Using Topographic Maps to Generate Topographic Profiles

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    Topographic maps are "plan-view" representations of Earth's three-dimensional surface. They are a standard type of map-view that provides an overhead, or aerial, perspective.

    Among the defining features of a topographic map are the contour lines that indicate locations of constant elevation. The elevation interval between the contour lines is dependent on the level of detail provided by the map and the kind of topography present. For example, regions with significant topographic variation might require contour lines separated by 40-100 ft., whereas generally flat-lying regions with little topographic variation might have more broadly separated 10-20 ft. contours. To an experienced user of such maps, the patterns made by the topographic lines are representative of various landform patterns, such as ridges, valleys, hills, and plateaus.

  • Earth Science

    08:54
    Making a Geologic Cross Section

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    Geologic maps were first made and utilized in Europe, in the mid-to-late 18th century. Ever since, they have been an important part of geological investigations all around the world that strive to understand rock distributions on the surface of the earth, in the subsurface, and their modification through time. A modern geologic map is a data-rich representation of rocks and rock-structures in a two-dimensional plan view. The base for most geologic maps is a topographic map, onto which color variations have been placed to represent specific rock units. The boundaries between the rock units are called contacts. In addition to the contact lines, geologic maps contain symbols that represent key features, such as the dip and strike of the rock units, anticlines and synclines, and the traces of fault surfaces. Although the two-dimensional map-view is useful, one of a geologist's key tasks is to infer the type and orientation of rocks in the subsurface. This is done using geologic rules, inferences, and projections downward from the surface. The result is a geologic cross section, a view that essentially provides a cutaway image, much like one would see on a canyon wall or in a roadcut. This hypothetical slice into the earth, providing a third dimension (depth), is the key to a host of geological applications. Cross sections are used to ass

  • Earth Science

    07:32
    Physical Properties Of Minerals I: Crystals and Cleavage

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    The physical properties of minerals comprise various measurable and discernible attributes, including color, streak, magnetic properties, hardness, crystal growth form, and crystal cleavage. Each of these properties are mineral-specific, and they are fundamentally related to a particular mineral’s chemical make-up and atomic structure.

    This experiment examines two properties that stem primarily from symmetric repetition of fundamental, structural atomic groupings, called unit cells, within a crystal lattice, a crystal growth form, and crystal cleavage. Crystal growth form is the macroscopic expression of atomic-level symmetry, generated by the natural growth process of adding unit cells (the molecular building blocks of minerals) to a growing crystal lattice. Zones of rapid unit-cell-addition become the edges between the planar surfaces, i.e. faces, of the crystal. It is important to recognize that rocks are aggregates of mineral grains. Most rocks are polymineralic (multiple kinds of mineral grains) but some are effectively monomineralic (composed of a single mineral). Because rocks are combinations of minerals, rocks are not referred to as having crystal form. In some cases, geologists refer to rocks as having a general cleavage, but here the term is simply used to refer to repetitive breaking surfaces and is not a

  • Earth Science

    07:16
    Physical Properties Of Minerals II: Polymineralic Analysis

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    The physical properties of minerals include various measurable and discernible attributes, including color, streak, magnetic properties, hardness, crystal growth form, and crystal cleavage. These properties are mineral-specific, and they are fundamentally related to a particular mineral’s chemical make-up and atomic structure.

    This video examines several physical properties that are useful in field and hand sample mineral identification— color, luster, streak, hardness, magnetism, and reaction with acid. Unlike crystal form and crystal cleavage, these properties are somewhat more closely linked to mineral chemical composition than to atomic structure, but both do play a role. It is important to recognize that rocks are aggregates of mineral grains. Most rocks are polymineralic (multiple kinds of mineral grains) but some are effectively monomineralic (composed of a single mineral). Unlike crystal form and cleavage, which are terms reserved for mineral specimens, geologists might on occasion refer to a rock as having a general sort of color, hardness, magnetism, or reaction with acid. In other words, the physical properties looked at here are potentially appropriate for use with rocks as well as with specific minerals.

  • Earth Science

    07:27
    Igneous Volcanic Rock

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    Igneous rocks are the products of cooling and crystallization of magma. Volcanic rocks are a particular variety of igneous rock, forming as a consequence of magma breaching the surface, then cooling and crystallizing in the subaerial environment. 

    Magma is liquid rock that typically ranges in temperature from approximately 800 °C to 1,200 °C (Figure 1). Magma itself is produced within the Earth via three primary melting mechanisms, namely the addition of heat, addition of volatiles, and decompression. Each mode of melt generation tends to produce specific types of magma and, therefore, distinct eruptive styles and structures. Figure 1. Fresh lava breakout on Kilauea, Hawaii. Lava is the term for magma that is on Earth’s surface.

  • Earth Science

    09:26
    Igneous Intrusive Rock

    Source: Laboratory of Alan Lester - University of Colorado Boulder

    Igneous rocks are products of the cooling and crystallization of high temperature liquid rock, called magma. Magmatic temperatures typically range from approximately 800 °C to 1,200 °C. Molten rock is, perhaps luckily for humans, an anomaly on planet Earth. If a random and imaginary drill hole were made in the Earth, it would most likely not reach a region of truly and totally molten material until the outer core, at nearly 2,900 km beneath the surface (Earth's radius is 6,370 km). Even there, this molten material would predominantly consist of liquid iron, not true silicate rock, and be incapable of ever reaching Earth's surface. Volcanic eruptions and igneous rocks do occur though, and they are evidence that there are indeed isolated regions of melting and magma generation within the Earth.

  • Earth Science

    08:27
    An Overview of bGDGT Biomarker Analysis for Paleoclimatology

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    Throughout this series of videos, natural samples were extracted and purified in search of organic compounds, called biomarkers, that can relate information on climates and environments of the past. One of the samples analyzed was sediment. Sediments accumulate over geologic time in basins, depressions in the Earth into which sediment flows through the action of fluid (water or air), movement, and gravity. Two main types of basins exist, marine (oceans and seas) and lacustrine (lakes). As one might guess, very different types of life live in these settings, driven in large part by the difference in salinity between them. Over the last few decades, organic geochemists discovered a toolbox of biomarker proxies, or compounds that can be used to describe climate or environment, some of which work in marine environments and some of which work in lacustrine. We turn our attention here to the lacustrine realm and branched glycerol dialkyl glycerol tetraethers (Figure 1). In this section we focus on analysis of terrestrial paleotemperature using branched glycerol dialkyl glycerol tetrathers (Figure 1; brGDGTs) and the MBT/CBT proxy. This proxy was initially described by Weijers et al.1 and is based on the distribution of ring and branch structures in brGDGTs. They found that the cyclization of branched tetraethers (CBT) was directly rel

  • Earth Science

    10:10
    An Overview of Alkenone Biomarker Analysis for Paleothermometry

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    Throughout this series of videos, natural samples were extracted and purified in search of organic compounds, called biomarkers, that can relate information on climates and environments of the past. One of the samples analyzed was sediment. Sediments accumulate over geologic time in basins, depressions in the Earth into which sediment flows through the action of fluid (water or air), movement, and gravity. Two main types of basins exist, marine (oceans and seas) and lacustrine (lakes). As one might guess, very different types of life live in these settings, driven in large part by the difference in salinity between them. Over the last few decades, organic geochemists discovered a toolbox of biomarker proxies, or compounds that can be used to describe climate or environment, some of which work in marine environments and some of which work in lacustrine. We turn our attention here to the marine realm and alkenone paleothermometry using the Uk'37 sea surface temperature proxy. The most well-established and widely applied open-ocean biomarker sea surface temperature (SST) proxy is Uk'37. Uk'37 = (C37:2) / (C37:2 + C37:3) (see Herbert1 for a review) The index is based on the ratio of two polyunsaturated long-chain alkyl ketones, called alkenones, produced by some classes of haptophyte algae2,3. Culture4,5 an

  • Earth Science

    07:22
    Sonication Extraction of Lipid Biomarkers from Sediment

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    The material comprising the living "organic" share of any ecosystem (leaves, fungi, bark, tissue; Figure 1) differs fundamentally from the material of the non-living "inorganic" share (rocks and their constituent minerals, oxygen, water, metals). Organic material contains carbon linked to a series of other carbon and hydrogen molecules (Figure 2), which distinguishes it from inorganic material. Carbon's wide valency range (-4 to +4) allows it to form up to four separate covalent bonds with neighboring atoms, usually C, H, O, N, S, and P. It can also share up to three covalent bonds with a single other atom, such as the triple bond in the often-poisonous cyanide, or nitrile, group. Over the past 4.6 billion years, this flexibility has led to an amazing array of chemical structures, which vary in size, complexity, polarity, shape, and function. The scientific field of organic geochemistry is concerned with the identification and characterization of the whole range of detectable organic compounds, called biomarkers, produced by life on this planet, as well as others, through geologic time. Figure 1. Organic material, such as trees, leaves, and moss, are chemically and visually distinct from inorganic material, such as pavement.

  • Earth Science

    08:03
    Soxhlet Extraction of Lipid Biomarkers from Sediment

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    Every lab needs standards that track the performance, accuracy, and precision of its instruments over time to ensure a measurement made today is the same as a measurement made a year from now (Figure 1). Because standards must test the performance of instruments over a long period of time, large volumes of the standards are often required. Many chemical standards can be purchased from retail scientific companies, like Sigma-Aldrich and Fisher. However, some compounds that occur in nature and that are relevant to paleoclimatic studies have not yet been isolated and purified for purchase. Therefore, these compounds need to be extracted from natural samples, and because of the large volumes of standards required, large volumes of sediment need to be extracted. The Accelerated Solvent Extraction (Dionex) and sonication extractions are not appropriate for the extraction of such large sediment volumes. In these circumstances, a Soxhlet extraction is used. Figure 1. Schematic depicting how chemical standard tracks the performance of an instrument through time. The dashed line represents a 1:1 relationship between the accepted and measured (on the instrument) value of a variable. Each star is a weekly measurement of the chemical standard. Green stars represent standards that are accurate. Red stars reflect those that are not accurate

  • Earth Science

    06:41
    Extraction of Biomarkers from Sediments - Accelerated Solvent Extraction

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    The distribution of a group of organic biomarkers called glycerol-dialkyl glycerol-tetraethers (GDGTs), produced by a suite of archaea and bacteria, were found in modern sediments to change in a predictable manner in response to air or water temperature1,2. Therefore, the distribution of these biomarkers in a sequence of sediments of known age can be used to reconstruct the evolution of air and/or water temperature on decadal to millennial timescales (Figure 1). The production of long high-resolution records of past climates, called paleoclimatology, depends on the rapid analysis of hundreds, possibly thousands of samples. Older extraction techniques, such as sonication or Soxhlet, are too slow. However, the newer Accelerated Solvent Extraction technique was designed with efficiency in mind. Figure 1. An example of a paleoclimate record showing changes in sea surface temperature (SST) in the eastern Mediterranean Sea during the past ~27,000 years3. This record comprises ~115 samples and is based on the isoprenoidal GDGT-based TEX86 SST proxy.

  • Earth Science

    08:28
    Conversion of Fatty Acid Methyl Esters by Saponification for Uk'37 Paleothermometry

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    The product of an organic solvent extraction, a total lipid extract (TLE), is often a complex mixture of hundreds, if not thousands, of different compounds. The researcher is often only interested in a handful of compounds or, if interested in many, may need to remove unwanted constituents that are"in the way" or co-eluting. For example, the concentrations of individual compounds in a sample are often determined on a gas chromatograph coupled to a flame-ionizing detector (GC-FID), because the relationship between FID response (in pA) and the amount of compound in a sample (e.g., ng/µL) is both linear and sensitive. The GC portion of the instrument separates different compounds in a sample based on their boiling point, chemical structure, and affinity with a solid phase that can change according to application. The result is a chromatogram (Figure 1), showing the separation of different chemical constituents in time, as well as their relative concentration (calculated as the area under the curve). However, sometimes more than one compound elutes off the GC at a time (Figure 1). In this case, sample purification is required before compounds can be confidently quantified.   Figure 1. A chromatogram showing the separation of different chemical constituents over time and their relative concentration (area und

  • Earth Science

    09:17
    Purification of a Total Lipid Extract with Column Chromatography

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    The product of an organic solvent extraction, a total lipid extract (TLE), is often a complex mixture of hundreds, if not thousands, of different compounds. The researcher is often only interested in a handful of compounds. The compounds of interest may belong to one of several classes of compounds, such as alkanes, ketones, alcohols, or acids (Figure 1), and it may be useful to remove the compound classes to which it does not belong in order to get a clearer view of the compounds you are interested in. For example, a TLE may contain 1,000 compounds, but the Uk'37 sea surface temperature proxy is based on only two compounds (alkenones) and the TEX86 sea surface temperature proxy is based on only four (glycerol dialkyl glycerol tetraethers). It would behoove the researcher to remove as many of the compounds they are not interested in. This makes the instrumental analysis of the compounds of interest (alkenones or GDGTs) less likely to be complicated by other extraneous compounds. In other cases, an upstream purification technique may have produced compounds you wish to now remove from the sample, such as the production of carboxylic acids during saponification in our previous video. In both of the above cases the purification technique called column chromatography is very useful. Figure 1. Geochemically important functiona

  • Earth Science

    07:51
    Removal of Branched and Cyclic Compounds by Urea Adduction for Uk'37 Paleothermometry

    Source: Laboratory of Jeff Salacup - University of Massachusetts Amherst

    As mentioned in previous videos, the product of an organic solvent extraction, a total lipid extract (TLE), is often a complex mixture of hundreds, if not thousands, of different compounds. The researcher is often only interested in a handful of compounds. In the case of our two organic paleothermometers (Uk'37 and MBT/CBT), the interest is in only 6 compounds (2 alkenones and 4 isoprenoidal glycerol dialkyl glycerol tetraethers). As discussed in the previous two videos in this series, purification techniques may be applied in order to pare down the number of compounds in an analyzed sample. These techniques may chemically alter the unwanted components (saponification), take advantage of the different compound chemistries (column chromatography), or use the different shapes and sizes of the molecules to include or exclude certain components from the analysis (urea adduction). The atomic structure of different chemicals leads some organic compounds to form long, narrow, straight chains (n-alkanes and alkenones), other organic compounds to form complex cyclic structures, others to form highly-branched structures, and yet others which form both cyclic and branched structures (GDGTs) (Figure 1). The different shapes and sizes of the compounds in a sample can be used to separate them from one another, in much the same way as a coin sor

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