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Understanding the Geology Map Layer: A Comprehensive Guide

Understanding the Geology Map Layer: A Comprehensive Guide

By Jeff Nazuka
June 12, 2024

Introduction to Geological Maps on AcreValue

AcreValue has introduced a comprehensive Geology Layer that provides users with detailed geological data across the entire continental United States. This feature is invaluable for landowners, researchers, developers, and hobbyists, offering insights into the geological characteristics of specific areas. The U.S. Geological Survey (USGS) Geologic map included in AcreValue provides essential information such as Age, Abbreviation, Rock Type, Lithology, and Other Notes.

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Understanding the USGS Geologic Map Categories

  • Age: Refers to the geological time period during which the rock or sediment was formed. This is crucial for understanding the history and development of the Earth's crust in that area.
  • Abbreviation: A shortened form of the geological age or formation name, used for easy reference on the map.
  • Rock Type: The classification of the rock based on its mineral composition and formation process (e.g., igneous, sedimentary, metamorphic).
  • Lithology: Describes the physical characteristics of the rock, such as grain size, texture, and composition.
  • Other Notes: Additional information that may include significant geological features, historical context, or important findings related to the area.

Example:

A map section might show:

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  • Age: Jurassic
  • Abbreviation: J
  • Rock Type: Sedimentary
  • Lithology: Sandstone, shale
  • Other Notes: Contains fossils of early reptiles
An example map section of the Geology Layer on AcreValue.
An example map section of the Geology Layer on AcreValue.

Geologic Layer Ages and Abbreviations

The USGS Geologic map includes various geological ages, each with its abbreviation and unique characteristics:

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  • Precambrian (Pc): The oldest geological era, spanning from the formation of Earth about 4.6 billion years ago to 541 million years ago. It includes rocks that are primarily igneous and metamorphic, and it's known for ancient minerals and early life forms like stromatolites.
  • Cambrian (Cm): From about 541 to 485 million years ago, this period is known for the "Cambrian Explosion" of diverse life forms, including trilobites and brachiopods. Sedimentary rocks like shale and limestone are common.
  • Ordovician (O): Spanning 485 to 443 million years ago, this period saw the diversification of marine life. Fossils of brachiopods, bryozoans, and the first fish can be found in sedimentary rocks like limestone and sandstone.
  • Silurian (S): From 443 to 419 million years ago, this period is known for the stabilization of Earth's climate and the appearance of coral reefs. Sedimentary rocks like limestone and dolomite are typical.
  • Devonian (D): Lasting from 419 to 359 million years ago, often called the "Age of Fishes," it includes fossils of early amphibians and land plants. Common rocks include sandstone, shale, and limestone.
  • Mississippian (M): Spanning 359 to 323 million years ago, this period is known for its extensive limestone deposits and marine life like crinoids and brachiopods.
  • Pennsylvanian (P): From 323 to 299 million years ago, it’s known for vast coal swamps and the first reptiles. Coal, shale, and sandstone are prevalent.
  • Permian (P): Lasting from 299 to 252 million years ago, it ended with the largest mass extinction. Limestone, sandstone, and evaporites like gypsum are common.
  • Triassic (Tr): From 252 to 201 million years ago, marking the rise of dinosaurs. Rocks include sandstone, conglomerate, and red beds.
  • Jurassic (J): Spanning 201 to 145 million years ago, famous for dinosaurs and the first birds. Sedimentary rocks like sandstone and shale dominate.
  • Cretaceous (K): Lasting from 145 to 66 million years ago, this period saw the peak of dinosaurs and the emergence of flowering plants. Common rocks include limestone, chalk, and shale.
  • Tertiary (T): From 66 to 2.6 million years ago, this period includes the rise of mammals. Sedimentary rocks like sandstone and conglomerate are prevalent.
  • Quaternary (Q): The most recent period, spanning from 2.6 million years ago to the present. Known for ice ages and human evolution, it includes glacial deposits and alluvium.

Rock Types and Descriptions

Geologic maps categorize rocks into several types:

  • Igneous Rocks: Formed from solidified magma or lava.
    • Intrusive (Plutonic) Igneous Rocks: Formed when magma cools slowly beneath the Earth's surface. Examples include granite (coarse-grained, usually light-colored) and diorite.
    • Extrusive (Volcanic) Igneous Rocks: Formed when lava cools quickly on the Earth's surface. Examples include basalt (fine-grained, usually dark-colored) and rhyolite.
  • Sedimentary Rocks: Formed from the accumulation and compaction of sediment.
    • Clastic Sedimentary Rocks: Made up of fragments of other rocks. Examples include sandstone (composed of sand-sized particles) and shale (composed of clay-sized particles).
    • Chemical Sedimentary Rocks: Formed from dissolved minerals precipitating out of solution. Examples include limestone (composed mainly of calcium carbonate) and evaporites like gypsum.
  • Metamorphic Rocks: Formed from the transformation of existing rock types under heat and pressure.
    • Foliated Metamorphic Rocks: Have a layered or banded appearance. Examples include schist and gneiss.
    • Non-foliated Metamorphic Rocks: Do not have a layered appearance. Examples include marble (metamorphosed limestone) and quartzite (metamorphosed sandstone).
  • Interlayered Rocks: These are sequences where different types of rocks (e.g., sedimentary and volcanic) are layered together. They provide important information about the depositional environment and geological history.

Lithology Types and Descriptions

Lithology refers to the physical characteristics of rocks, which are important for identifying and understanding geological formations:

  • Granite: A coarse-grained, intrusive igneous rock composed mainly of quartz, feldspar, and mica.
  • Basalt: A fine-grained, extrusive igneous rock rich in iron and magnesium.
  • Sandstone: A clastic sedimentary rock composed of sand-sized mineral particles or rock fragments.
  • Shale: A fine-grained clastic sedimentary rock composed of clay-sized particles.
  • Limestone: A chemical sedimentary rock composed mainly of calcium carbonate, often formed from marine organisms.
  • Dolomite: Similar to limestone but contains magnesium as well as calcium carbonate.
  • Gypsum: An evaporite mineral often found in sedimentary environments.
  • Coal: An organic sedimentary rock formed from plant debris.
  • Marble: A non-foliated metamorphic rock formed from limestone.
  • Schist: A foliated metamorphic rock with a pronounced schistosity, composed mainly of mica.
  • Quartzite: A non-foliated metamorphic rock formed from sandstone.
  • Conglomerate: A clastic sedimentary rock composed of rounded fragments set in a finer matrix.
  • Mafic Rocks: Dark-colored igneous rocks rich in magnesium and iron. Examples include basalt and gabbro.
  • Felsic Rocks: Light-colored igneous rocks rich in silica and aluminum. Examples include granite and rhyolite.

Using the Geologic Map with Other AcreValue Features

Users can enhance their land analysis by integrating the Geology Layer with other features on AcreValue:

  • Soil Maps: Combine geological data with soil maps to assess the suitability of land for agriculture or construction.
  • Land Value Analysis: Use geological information to understand how underlying rock types may affect property value, especially for mineral rights or potential hazards.
  • Environmental Assessments: Evaluate potential environmental impacts and conservation needs based on the geology of the area.

Leveraging the Geological Maps for Different Users

Landowners and Developers:

  • Resource Identification: Identify potential areas for drilling, mining, or other resource extraction.
  • Construction Planning: Assess the stability and suitability of the land for building projects.

Researchers and Geologists:

  • Field Studies: Plan and conduct field studies with precise geological data.
  • Historical Research: Understand the geological history and evolution of specific regions.

Rockhounds and Hobbyists:

  • Rock Hounding: Use geological maps to find areas rich in specific minerals or fossils.
  • Contacting Landowners: Utilize AcreValue’s parcel owner information to request permission for rock hounding on private property.

How to Access the Geology Layer on AcreValue

Accessing the new Geology Layer on AcreValue is straightforward:

  1. Navigate to the Map: Open the AcreValue platform and go to the map view.
  2. Open the Map Layers: Click on the map layers icon to view available layers.
  3. Toggle the GeoScience Category: Find and select the GeoScience category to enable the Geology Layer.

Once enabled, you can explore the geological features of any area in the continental U.S., making your research and planning more informed and precise.

AcreValue Map with Map Layer Panel expanded and Geology selected
AcreValue Map with Map Layer Panel Expanded and Geology Selected

By leveraging the new Geology Layer on AcreValue, users can unlock a wealth of geological information, enhancing their research, land-use planning, and recreational activities. Start exploring today and discover the hidden geological treasures on your land!

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The content and information provided in this communication are for general informational purposes only. It is not intended as financial, investment, or legal advice and should not be construed as such. Always consult with a qualified financial advisor, lawyer, or professional before making any financial decisions. The user acknowledges that any reliance on the information provided is at their own risk, and AcreValue shall not be held liable for any actions taken based on the content herein.
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