Earth Science Essential Understandings and Knowledge ES 1 and 2: Scientific Investigation Density - density expresses the relationship between mass and volume D=M/V Scientific Investigation - information and data collected can be organized and expressed in the form of charts, graphs, and diagrams - changing relevant variables will generally change the outcome - a hypothesis can be supported, modified, or rejected based on collected data. Hypotheses are tentative explanations that account for a set of facts and can be tested by further investigations - experiments are designed to test hypotheses - scientific laws are generalizations of observational data that describe patterns and relationships – laws may change as new data become available – scientific theories are systematic sets of concepts that offer explanations for observed patterns in nature – theories provide frameworks for relating data and guiding future research – theories may change as new data become available - conclusions are only as good as the quality of the collected data - any valid hypothesis can be tested - any valid scientific theory has passes tests designed to invalidate it - a hypothesis can be supported, modified, or rejected cased on collected data - experiments are designed to test hypotheses - there can be more than one explanation for any phenomena Earth System - earth is a dynamic system, and all atmospheric, geological, and oceanographic processes interrelate and influence one another - the core, mantle, and crust of earth are dynamic systems, constantly in motion - the earth consists of a solid, mostly iron inner core; a liquid, mostly iron outer core; a rocky, plastic mantle; and a rocky, brittle crust ES 3: Maps and Globes Mapping - scale relates to actual distance - topographic maps, air photos, and satellite images relate to actual 3-D landforms - grid systems are used to define locations and directions on maps, globes, and charts ES 5 and 6: Rocks and Minerals Minerals - there is a difference between rock and minerals - minerals can be identified based on specific chemical and physical properties - minerals are important to human wealth and welfare - a mineral is naturally occurring, inorganic, solid substance with a definite chemical composition and structure - minerals may be identified by their physical properties such as hardness, color, luster, and streak - most rocks are made of one or more minerals - some major rock-forming minerals are quartz, feldspar, calcite, and mica - ore minerals include pyrite, magnetite, hematite, galena, graphite, and sulfur - the major elements found in earth’s crust are oxygen, silicon, aluminum, and iron – the most abundant group of minerals is the silicates, which contain silicon and oxygen Rocks - rocks can be identified on the basis of mineral content and texture - the process by which they are formed define the three major groups of rocks - the rock cycle is the process by which all rocks are formed and how basic earth materials are recycled through time - igneous rock forms from molten rock that cools and hardens either below or on earth’s surface - sedimentary rocks may either form from rock fragments or organic matter bound together or they are formed by chemical precipitation - metamorphic rocks form when any rock is changed by the effects of heat , pressure, or chemical action - extrusive igneous rocks have small or no crystals resulting in fine-grained or glassy textures - intrusive igneous rocks have larger crystals and a coarser texture - extrusive igneous rocks include pumice, obsidian, and basalt - intrusive igneous rocks include granite - sedimentary rocks are clastic or chemical - clastic sedimentary rocks are made up of fragments of other rocks and include sandstone, conglomerate, and shale - non-clastic sedimentary rocks include limestone and rock salt - metamorphic rocks can be foliated or unfoliated (non-foliated) - foliated metamorphic rocks have bands of different minerals – slate, schist, and gneiss are foliated metamorphic rocks - unfoliated metamorphic rocks have little or no banding and are relatively homogenous throughout – marble and quartzite are unfoliated metamorphic rocks ES 7: Natural Resources Renewable and Non-renewable Resources - resources are limited and are either renewable or non-renewable - there are advantages and disadvantages to using any energy source - Virginia has many natural resources - modern living standards are supported by extensive use of both renewable and non-renewable resources - extraction and use of any resource carries an environmental cost that must be weighed against economic benefit - renewable resources can be replaced by nature at a rate close to the rate at which they are used – renewable resources include vegetation, sunlight, and surface water - non-renewable resources are renewed very slowly or not at all – non-renewable resources include coal, oil, and minerals - fossil fuels are non-renewable and may cause pollution, but they are relatively cheap and easy to use - in Virginia, major rock and mineral resources include coal for energy, gravel and crushed stone for road construction, and limestone for making concrete ES 9: Freshwater Resources Soils - soil is formed from weathering of rocks and organic activity - soil is loose rock fragments ad clay derived from weathered rock mixed with organic material Karst Topography - karst topography is developed in area underlain by carbonate rocks including limestone and dolomite - karst topography included features like caves and sinkholes - karst topography forms when limestone is slowly dissolved away by slightly acidic groundwater - where limestone is abundant in the Valley and Ridge province of Virginia, Karst topography is common ES 8: Plate Tectonics, Volcanoes, Earthquakes, and Mountains Virginia Geologic History - Virginia has a billion-year long tectonic and geologic history - Virginia has five physiographic provinces produced by past tectonic and geologic activity - each province has unique physical characteristics resulting from its geologic past - geologic processes produce characteristic structures and features - the five physiographic provinces are Coastal Plain, Piedmont, Blue Ridge, Valley and Ridge, and Appalachian Plateau - the Coastal Plain is a flat area underlain by young, unconsolidated sediments – these layers of sediment were produced by erosion of the Appalachian Mountains and then deposited on the Coastal Plain - the Piedmont is an area of rolling hills underlain by mostly ancient igneous and metamorphic rocks – the igneous rocks are the roots of volcanoes formed during an ancient episode of subduction that occurred before the formation of the Appalachian Mountains - the Blue Ridge is a high ridge separating the Piedmont from the Valley and Ridge province – the billion-year old igneous and metamorphic rocks of the Blue Ridge are the oldest in the state – some metamorphism of these rocks occurred during the formation of the Appalachian Mountains - the Valley and Ridge province is an area with long parallel ridges and valleys underlain by ancient folded and faulted sedimentary rocks – the folding and faulting of the sedimentary rocks occurred during a collision between Africa and North America – the collision, which occurred in the late Paleozoic era, produced the Appalachian Mountains - the Appalachian Plateau has rugged, irregular topography and is underlain by ancient, flat-lying sedimentary rocks – the area is actually a series of plateaus separated by faults – most of Virginia’s coal resources are found in the plateau province Weathering, Erosion, and Deposition - weathering, erosion and deposition are inter-related processes - weathering is the process by which rocks are broken down chemically and physically by the action of water, air, and organisms - erosion is the process by which earth materials are transported by moving water, ice, or wind - deposition is the process by which earth materials carried by wind, water, or ice settle out and are deposited Plate Tectonic Processes - the core, mantle, and crust of earth are dynamic systems, constantly in motion - the earth consists of a solid, mostly iron inner core; a liquid, mostly iron outer core; a rocky, plastic mantle; and a rocky, brittle crust - most geologic activity (earthquakes, volcanoes, and mountain building) occurs as a result of relative motion along plate boundaries - plate motion occurs as a consequence of convection currents in the mantle – plate tectonics is driven by convection currents in the earth’s mantle - relative plate motions and plate boundaries are convergent (subduction and continental collision), divergent (sea-floor spreading), or transform - there are two different types of crust (oceanic and continental) that have very different characteristics - earthquake activity is associated with all plate boundaries - major features of convergent boundaries include collision zones (folded and thrust-faulted mountains) and subduction zones (volcanoes and trenches) - major features of divergent boundaries include mid-ocean ridges, rift valleys, and fissure volcanoes - major features of transform boundaries include strike-slip faults - a fault is a break or crack in earth’s crust along which movement has occurred - most active faults are located at or near plate boundaries - earthquakes result when movement occurs along a fault - when rocks are compressed horizontally, their layers may be deformed into wave-like forms called folds – this commonly occurs during continental collisions - a volcano is an opening where magma is erupted onto earth’s surface - most volcanic activity is associated with subduction, rifting, or sea-floor spreading Groundwater - a substantial amount of water is stored in permeable soil and rock underground - permeability is a measure of the ability of a rock or sediment to transmit water or other liquids - water does not pass through impermeable materials - earth’s fresh water supply is finite - water is continuously being passed through the hydrologic cycle - fresh water is necessary for survival and most human activities - geological processes, such as erosion, and human activities, such as waste disposal, can pollute water supplies - the three major regional watershed systems in Virginia lead to the Chesapeake Bay, the North Carolina Sounds, and the Gulf of Mexico ES 10: Geologic Time, Fossils, and Dating Fossils - evidence of ancient, often extinct life is preserved in many sedimentary rocks - fossil evidence indicates that life forms have changed and become more complex over geologic time - a fossil is the remains, impressions, or other evidence of former existence of life preserved in rock - some ways in which fossils can be preserved are molds, casts, and original bone or shell - nearly all fossils are found in sedimentary rocks - in Virginia, fossils are found mainly in the Coastal Plain, Valley and Ridge, and Appalachian Plateau provinces - most Virginia fossils are of marine organisms – this indicates that large areas of the state have been periodically covered by seawater - Paleozoic, Mesozoic, and Cenozoic fossils are found in Virginia Dating - earth is very ancient, about 4.6 billion years old - the history of earth and the ages of rocks can be investigated and understood by studying rocks and fossils - relative time places events in a sequence without assigning any numerical ages - fossils, superposition, and crosscutting relations are used to determine the relative ages of rocks - absolute time places a numerical age on an event - radioactive decay is used to determine the absolute age of rocks ES 11: Oceanography Physical and Chemical - the ocean is a dynamic system in which many chemical, biological, and physical changes are taking place - most waves on the ocean surface are generated by wind - the tides are the daily, periodic rise and fall of water level caused by the gravitational pull of the sun and moon - there are large current systems in the oceans that carry warm water towards the poles and cold water towards the equator - sea level falls when glacial ice caps grow and rises when the ice caps melt - upwelling bring cold, nutrient-rich water from the deep ocean to the surface and are areas of rich biological activity - estuaries, like the Chesapeake bay, are areas where fresh and salt water mix, producing variations in salinity and high biological activity Environmental and Geological - the oceans and environmentally and economically important - human activities and public policy have important consequences for the oceans - the oceans’ resources are finite and should be utilized with care - the impact of human activities such as waste disposal, construction, and agriculture affect the water quality within watershed systems and ultimately the ocean - algae in the oceans are an important source of atmospheric oxygen - the ocean are an important source of food and mineral resources as well as a venue for recreation and transportation - pollution and over-fishing can harm or deplete valuable resources - chemical pollution and sedimentation are great threats to the chemical and biological well being of estuaries and oceans System Interactions - convection is the major mechanism of energy transfer in the oceans, atmosphere, and earth’s interior - the ocean is the single largest reservoir of heat at earth’s surface - the stored heat in the ocean drives much of earth’s weather - the stored heat in the ocean causes climate near the ocean to be milder than climate in the interior of continents Seafloor Features - the topography of the seafloor is at least as variable as that on the continents - features of the seafloor that are related to plate tectonic processes include mid-ocean ridges and trenches - other major topographic features of the oceans are continental shelves, continental slopes, abyssal plains, and sea mounts ES 12 and 13: Meteorology Atmosphere - the composition of earth’s atmosphere has changed over geologic time - the early atmosphere contained little oxygen and more carbon dioxide than the modern atmosphere - early photosynthetic life such as cyanobacteria (blue-green algae) consumed carbon dioxide and generated oxygen - it was only after early photosynthetic life generated oxygen that animal life became possible - earth’s atmosphere is unique in the solar system in that it contains substantial oxygen - earth’s atmosphere is 21 percent oxygen, 78 percent nitrogen, and 1 percent trace gases - the atmosphere of Venus is mostly carbon dioxide and very dense - the atmosphere of Mars is very thin and mostly carbon dioxide - the composition of the atmosphere can change due to human, biologic, and geologic activity - human activities have increased the carbon dioxide content of the atmosphere - man-made chemicals have decreased the ozone concentrations in the upper atmosphere - volcanic activity and meteorite impacts can inject large quantities of dust and gases into the atmosphere - the ability of earth’s atmosphere to absorb and retain heat is affected by the presence of gases like water vapor and carbon dioxide Weather and Climate - weather and climate are different - weather describes day-to-day changes in atmospheric conditions - climate describes the typical weather patterns for a given location over a period of many years - the amount of energy reaching any given point on earth’s surface is controlled by the angle of sunlight striking the surface and varies with the seasons - areas near the equator receive more of the sun’s energy per unit area than areas nearer the poles - the conditions necessary for cloud formation are: air is at or below dew point and condensation nuclei are present – cloud droplets can join together to form precipitation - winds are created by uneven heat distribution at earth’s surface and modified by the rotation of earth - the coriolis effect causes deflections of the atmosphere due to the rotation of earth – global wind patterns result from the uneven heating of earth by the sun and are influenced by the coriolis force - the four major factors affecting climate are latitude, elevation, proximity to bodies of water, and position relative to mountains - energy transfer between earth’s surface and the atmosphere creates the weather - both weather and climate are measurable, and to a certain extent, predictable - convection is the major mechanism of energy transfer in the oceans, atmosphere, and earth’s interior - convection in the atmosphere is a major cause of weather - earth’s major climatic zones are the polar, temperate, and tropical zones - a tornado is a narrow, funnel-shaped column of spiral winds that extends downward from the cloud base toward earth - a hurricane is a tropical cyclone (counterclockwise movement of air) characterized by sustained winds of 120 kilometers per hour (75 miles per hour) or greater ES 4 and 14: Astronomy Earth - earth is one of nine planets in the solar system - earth is the third planet from the sun and is located between the sun and the asteroid belt – it has one natural satellite – the moon - earth revolves around the sun, tilted on its axis, causing seasons (equinoxes and solstices) - the moon revolves around earth creating the moon phases and eclipses - solar eclipses occur when the moon blocks out sunlight from earth’s surface, while lunar eclipses occur when earth blocks sunlight from reaching the moon’s surface - the tides are the daily, periodic rise and fall of water level caused by the gravitational pull of the sun and moon - water occurs on earth as a solid (ice), a liquid (water), or a gas (water vapor) due to its position in the solar system Solar System - the solar system consists of many types of celestial bodies - the sun consists largely of hydrogen gas – its energy comes from nuclear fusion of hydrogen to helium - there are essentially two types of planets in our solar system - the four inner (terrestrial) planets consist mostly of solid rock - four of the outer planets are gas giants, consisting of thick outer layers of gaseous materials, perhaps with small rocky cores - the fifth outer planet, Pluto, has an unknown composition, but appears solid - moons are natural satellites of planets that vary widely in composition - comets orbit the sun and consist mostly of frozen gases - asteroids are rocky or metallic iron objects ranging in size from millimeters to kilometers – they are the source of most meteorites - much of our knowledge about the solar system is a result of space exploration efforts – these efforts continue to improve our understanding of the solar system - Apollo 11 was the first manned landing on the moon - the Hubble Space telescope has greatly improved our understanding of the universe - the universe is vast and very old - the big bang theory is our best current model for the origin of the universe - the big bang theory states that the universe began in a very hot dense state that expanded and eventually condensed into galaxies - the solar nebular theory is our best current idea for the origin of the solar system - the solar nebular theory explains that the planets formed through condensing of the solar nebula - stars have a finite lifetime and evolve over time - stars form by condensation of interstellar gas - the mass of a star controls its evolution, length of its lifetime, and ultimate fate - the Hertzsprung-Russell diagram illustrates the relationship between the absolute magnitude and the surface temperature of stars – as stars evolve, their position on the Hertzsprung-Russell diagram - galaxies are collections of billions of stars – the basic types of galaxies are spiral, elliptical, and irregular - the solar system is located in the Milky Way galaxy - the basic types of galaxies are spiral, elliptical, and irregular - a light-year is the distance light travels in one year and is the most commonly used measurement for distance in astronomy - much of our information about our galaxy and the universe comes from ground-based observations