Geology Facts U.S.Departmentofthe InteriorU.S.GeologicalSurveyContact:Kate BartonLastModification:18 Oct2000 (ebj)USGS Privacy Policy U.S.Departmentofthe InteriorU.S.GeologicalSurveyContact:Kate BartonLastModification:18 Oct2000 (ebj)USGS Privacy Policy For more information, please visit: Virginia Division of Mineral Resources Virginia Division of Mineral Resources State's rock-ages colored below For more information, please visit: Virginia Division of Mineral Resources Virginia Division of Mineral Resources State's rock-ages colored below U. U.

SOL 8 The student will investigate and understand how freshwater resources are influenced by geologic processes and the activities of humans. Key concepts include: processes of soil development; development of karst topography; relationships between groundwater zones, including saturated and unsaturated zones, and the water table; identification of sources of fresh water including rivers, springs, and aquifers, with reference to the hydrologic cycle; dependence on freshwater resources and the effects of human usage on water quality; and identification of the major watershed systems in Virginia, including the Chesapeake Bay and its tributaries. Essential questions How do weathering, erosion, and deposition (sedimentation) affect the surface of the Earth? How does Earth’s water supply change? Why is the conservation of soil important ?

What you have to know Factors – speed, volume, slope influence cutting ability – meanders. 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. Weathering, erosion, and deposition are interrelated processes. Weathering accelerates erosion and thus increases the rate of deposition. The potential for erosion is greatest in areas of high relief. The potential for deposition is greatest in areas of low relief, especially in standing water and in the ocean. Permeability is a measure of the ability of a rock or sediment to transmit water or other liquids. A substantial amount of water is stored in permeable soil and rock underground. Water does not pass through impermeable materials. 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. Karst topography is developed in areas underlain by carbonate rocks, including limestone and dolomite. Where limestone is abundant in the Valley and Ridge province of Virginia, karst topography is common. Karst topography forms when limestone is slowly dissolved away by slightly acidic groundwater. Karst topography includes features like caves and sinkholes.

Soil is formed from the weathering of rocks and organic activity. Soil is loose rock fragments and clay derived from weathered rock mixed with organic material. Running water is the major cause of erosion. Down slope movement of Earth materials is caused by gravity. Features of erosion and deposition caused by waves include deltas, beaches, and sandbars. Features of erosion and deposition caused by glaciers include U-shaped valleys, lakes, and moraine. Features of erosion and deposition caused by wind include blowouts, dunes and loess. Virginia’s Coastal plain consists of young unconsolidated sediments eroded from the western higher elevations. Virginia’s coast line is shaped by the action of waves. The composition and structure of soil are dependent on the resources, topography and climate. Renewable resources can be replaced by nature at a rate close to the rate at which they are used. Water is a renewable resource. Explain the types of deposition specific to streams and rivers (such as alluvial fans and deltas).

Destructive Geology Chemical weathering occurs mainly in warm, humid climates

Weathering can occur as either a mechanical or chemical process

Erosion is the process of materials being transported by moving water, ice, wind, or gravity

Streams and moving water are the major agents of erosion

Deposition is the dropping or settling out of sediments

High erosion= high relief areas, high deposition= low relief areas

Large particles settle out first, sediment size from largest to smallest- sand, silt, clay

As particle size increases, permeability increases (ability to hold water). Permeability is the ability of a material to drain

Porosity is the amount of pore space in a rock or sediment Different grain sizes and packing arrangements result in different porosity values. Top: individual pore spaces decrease in size with decreasing grain size. Bottom: porosity varies with packing (arrangement) of grains.

Soil evolution starts with the weathering of bedrock Organic material must be present in order to have soil. (humus)

Soil profiles consist of 3 horizons: O topsoil (humus) most evolved, A less humus, leaching of minerals from A, and B weathered rock C These layers are on top of bedrock

Groundwater layers from the surface down would include zone of aeration, water table, and zone of saturation

An aquifer is a layer of rock that transports groundwater freely A spring is an area where the water table reaches land’s surface

The Earth’s water supply is renewable but also finite

Karst topography has caves and sinkholes produced by acidic groundwater dissolving limestone

The watersheds of Virginia are the Sounds of North Carolina, the Chesapeake Bay, and the Atlantic Ocean.

Name the 3 main watersheds.

This depositional feature is found in the desert is best identified as a 1 a delta3. alluvial fan 2 sedimentary rock4 mass movement

What you need to know Virginia has five physiographic provinces produced by past tectonic and geologic activity. Each province has unique physical characteristics resulting from its geologic past. The five physiographic provinces of Virginia 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. Western boundary is the fall line with its characteristic elevation change and waterfalls.

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 (converging plates) 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 (regional due to converging plates) 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. Karst Topography (caves) and fossils are abundant

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.

ES.9The student will investigate and understand that many aspects of the history and evolution of Earth and life can be inferred by studying rocks and fossils. Key concepts include traces and remains of ancient, often extinct, life are preserved by various means in many sedimentary rocks; superposition, cross-cutting relationships, index fossils, and radioactive decay are methods of dating bodies of rock; absolute and relative dating have different applications but can be used together to determine the age of rocks and structures; and rocks and fossils from many different geologic periods and epochs are found in Virginia.

In order to meet this standard, it is expected that students will describe how life has changed and become more complex over geologic time. interpret a simple geologic history diagram, using superposition and cross-cutting relations. analyze how radioactive decay provides a reliable method to determine the age of many types of organic and inorganic materials. analyze the impact and role of global catastrophes (including asteroid/comet impacts, volcanism, continental collisions, climate collapse) on extinctions and evolution. analyze and interpret complex cross sections using both relative and absolute dating to unravel and define the geologic history of the section. The history of Earth and the ages of rocks can be investigated and understood by studying rocks and fossils. Evidence of ancient, often extinct life is preserved in many sedimentary rocks. A fossil is the remains, impression, or other evidence preserved in rock of the former existence of life. Fossil evidence indicates that life forms have changed and become more complex over geologic time. Some ways in which fossils can be preserved are molds, casts, and original bone or shell. Relative time places events in a sequence without assigning any numerical ages. Fossils, superposition, and cross-cutting 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. Earth is about 4.6 billion years. Paleozoic, Mesozoic, and Cenozoic fossils are found in Va. 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.

A fossil is the remains, impressions, or just the evidence of life preserved in rock

Virginia’s fossils are mostly marine and are from all eras in history

The Principle of Superposition states that the oldest rocks are found on the bottom of strata and the youngest are found on top

The Principle of Cross-cutting relationships state that an igneous intrusion is younger than the layers it cuts across

Fossils, Superposition, and Cross-cutting relationships are used to determine relative ages

Relative ages are placing events in sequence without assigning exact numerical ages

Absolute age gives numerical age to an event

Radioactive decay or half-life is used to determine the absolute age of rocks Radioactive isotope Daughter isotope Half-life (Myrs) Applications Carbon 14 Nitrogen Formerly living material less than 30,000 yo Uranium 235 Lead Lunar samples, meteorites, pre-Cambrian rocks Potassium 40 Argon Ocean floor basalts, lava flows, some sediment. Uranium 238 Lead Lunar samples, meteorites, pre-Cambrian rocks Rubidium 87 Strontium 8747,000 Very old rocks, similar to Uranium 1.Uranium dating is used to find the ages of the oldest rocks. 2.Carbon-14 is used to find the ages of human artifacts.

The Earth is about 4.6 billion years old

Enough is enough……….. Remember: Make sure you understand the question Read all the answers Slash the trash, get rid of the ones you know are not the answer When you are left with 2 answers, use the one that was your first choice