Backyard Geology: A Guide for Homeowners and Families

nkats, Feb 21, 2022

A child uses a little shovel to help his parents dig in the yard.

Studying geology can be both fun and beneficial, but many amateurs have difficulty finding the time and resources to conduct hands-on field experiments, especially while trying to balance work and family obligations. If you or someone in your family has a passion for geology, this may be a familiar problem, but it is easier than you think to study the planet without leaving the comfort of your property.

Through backyard geology, you can discover new minerals, learn about the history of the earth, and pique your curiosity without the need for travel, training, or specialized equipment. In this guide, we’ll go over the fundamentals of backyard geology, from the tools you’ll need to the rocks you’ll likely find. We’ll also discuss how to dig safely in your yard, and how to use geological knowledge to inform smarter real-estate decisions.

Introduction to Geology

Geology is defined as the study of the structure, evolution, and dynamics of the Earth and its natural mineral and energy resources. Geologists study the materials that make up the earth, as well as the planet’s history of environmental events like earthquakes, landslides, and volcanic eruptions. Some of the most common processes in geology include collecting samples in the field, conducting laboratory research, and mapping out geological features like ore deposits.

The information provided by geologists has a wide range of applications in modern industries, and plays an important role in how we use the earth’s resources. Geological research helps us understand how to safely build important structures and how to locate valuable natural resources like coal and fossil fuels within the earth. A fundamental component of this research is the analysis of minerals; including their physical properties, chemical makeup, and how they are formed.

Minerals

The study of minerals is the foundation of geology. According to the U.S. National Parks Service, a mineral is a homogeneous solid that can be made of a single native element or more usually a compound. Minerals are crucial components of the rocks, sands, and soils that make up the earth’s ecosystems. Some of the most common types of minerals on earth include quartz, micas, calcite, and fluorite. Geologists define minerals based on five fundamental characteristics, and use six physical traits to categorize them.

5 Characteristics of All Minerals

While there are many different minerals in geology, and each has varying physical properties, all types of minerals generally share the same five characteristics. Understanding these can help you more easily locate and analyze the minerals in your yard :

  • Naturally-Occurring: Minerals must be formed by natural processes, man-made materials like steel are not minerals because they are not found naturally in the earth.
  • Inorganic: Minerals cannot be living, and their existence cannot be dependent on the products of organic life. For example, coal is not a mineral because it is formed from fossilized plants.
  • Homogeneously Solid: Minerals must have consistently predictable properties, down to and including the atomic level.
  • Typical Ordered Internal Structure: The atoms of a mineral must be arranged in a repeating geometric pattern.
  • Definite Chemical Composition: A mineral must have the same chemical composition and the ratio of atoms everywhere it occurs.

Physical Properties of Minerals

The ability to properly identify minerals based on their physical properties is hugely important in backyard geology, as more precise methods like chemical testing may not be accessible to all amateurs. Geologists use six major physical traits to analyze, describe, and categorize minerals.

  • Cleavage: Brittleness, or the tendency of the mineral to break along weak points
  • Color: Some minerals have a distinct color, while others can vary in color
  • Hardness: The mineral’s level of scratch resistance, measured by the Mohs Scale. On the Mohs scale, a diamond is a ‘10’ while talc is a ‘1’.
  • Luster: The way that light reflects off the mineral’s surface. A mineral’s luster can be described as metallic, glassy, dull, or earthy.
  • Streak: The color of the residue left by scratching a mineral on a hard, white surface like chalk or porcelain.
  • Specific Gravity: The density of the mineral relative to an equal volume of water.

By using these metrics, professional and amateur geologists alike can identify and classify minerals with greater accuracy. Understanding the properties of minerals is critical for understanding the different types of rocks and the geological processes that lead to their formation.

Rocks

A rock is a solid mass that is made up of one or more minerals. Rocks are classified according to the minerals they contain, their chemical composition, and how they are formed. There are three categories of rock in geology, each with its own distinct chemical and physical properties.

Igneous

Igneous rocks, sometimes called magmatic rocks, are formed when molten rock (magma or lava) cools and solidifies. The magma that forms igneous rocks often comes from parts of the earth’s mantle or crust that have melted due to rising temperatures or decreasing pressure. Igneous rocks tend to have little texture, and some types may not be identifiable without chemical testing. Their exact texture and appearance can be granular or smooth, depending on their cooling conditions. They are commonly black, gray, or white in color. Some of the most common types of igneous rocks include obsidian, andesite, pumice, tuff, rhyolite, and basalt.

Sedimentary

Sedimentary rocks are formed when particles settle out of the air or water and accumulate in layers. The particles that form these rocks can come from minerals or organic matter. Because of the way they’re formed, sedimentary rocks often contain distinct layers with different colors or shades. These rocks are most commonly found on or close to the earth’s surface. According to the Geological Society of America, approximately two-thirds of all the exposed rocks on the earth’s surface are sedimentary. The most common types of sedimentary rock include sandstone, limestone, shale, and siltstone.

Metamorphic

Metamorphic rocks are formed when existing rocks are physically and chemically changed by an increase in pressure or heat. This process, known as metamorphosis, can happen to igneous and sedimentary rocks as well as existing metamorphic rocks. Metamorphic rocks are often formed deep beneath the earth’s surface, where the temperatures and pressure are much higher. Metamorphosis can cause rocks to recrystallize and take on a new texture or mineral composition, leading to dramatic changes in appearance. Because of this, metamorphic rocks are crystalline and typically have a layered or foliated texture. Some common types of metamorphic rocks include granite, phyllite, quartzite, and marble.

What Can You Expect to Find?

No matter what part of the country you live in, there will likely be some interesting specimens on your property, but the quantity and the exact type of rocks you’ll find will often depend on your location. To get an idea of what’s under your yard before you start digging, it may be helpful to research the unique geologic structure and history of your area, either by reading up on the subject or looking at a geological map of your region.

Along with geological structure and history, additional factors like climate and elevation can have a major impact on a region’s rock formation patterns over time. While some rocks are common throughout the U.S., other types are more prevalent in particular areas of the country.

In the Northeast, for example, some of the most common rock types are anorthosite, diorite, dolomite, sandstone, limestone, and quartzite. Whereas if you live in the Southwest, you’re more likely to find rocks like andesite, basalt, arkose, gypsum, or halite. Of course, it’s difficult to know exactly what you’ll discover before you get started, and the best way to learn is by collecting rocks and identifying your findings.

Identifying Backyard Rocks

In many cases, the various types of rock you find will be difficult to identify with the naked eye, and a detailed inspection will be required to accurately tell them apart. When you discover an unfamiliar rock in your yard, several steps can help you determine what it is:

  • Clean them: Backyard rocks often appear worn and dirty when you first dig them up. Scrubbing and washing them with clean water can help you get a clearer look at what you have.
  • Compare Them: One of the simplest ways to identify a newly found rock is by comparing it to any existing specimens that you already have identified. It’s important to note how the color, texture, and other physical properties of the new rock compare to the samples.
  • Examine them closely: Some properties of a rock; such as graining, can tell us a lot, but are difficult to examine with the naked eye. Viewing your rocks up close with a magnifying glass will help you better analyze these subtle features.
  • Perform a scratch test: Hardness is a very important metric for studying and identifying rocks. To measure the hardness of a rock, try to scratch its surface using a progressively harder series of objects. Softer rocks can be often visibly scratched with a fingernail, whereas harder materials like diamonds are nearly impossible to scratch.
  • Test for magnetization: Some types of igneous and metamorphic rocks contain small pieces of a magnetic mineral called lodestone, and will naturally attract iron. Conducting a simple attraction test with a small piece of iron can help you determine if the rocks you find are magnetized.

Basic Tools to Use for Backyard Geology

Before you start finding and identifying rocks, it’s important to have the right supplies on hand. While scientific studies often require specialized equipment, many of the tools used in backyard geology are common items that you may already have in your home:

  • Digging tools (shovels, hand trowels, etc.)
  • Durable gloves
  • Safety Glasses
  • Magnifying glass or lens
  • Sifting pan or sieve. A kitchen strainer can work in place of this
  • Water
  • Soft cloths or paper towels
  • Iron nail ‘
  • Magnet
  • Small containers for samples
  • Pen and paper
  • Sticky notes

Choosing a Dig Site

Once you have all the necessary equipment on hand, the next step is deciding where to dig. The area where you choose to dig can determine how many rocks you will find. When selecting a digsite, it’s helpful to first identify any spots on your property that may have higher rock or mineral concentrations. To locate an optimal digsite, look for rocky patches on the surface of your front or back yard.

Natural running water sources like creeks or streams are also ideal dig sites. This is because the erosion caused by running water can break down bedrock over time and expose interesting specimens hidden underneath. Once they become loose, rocks are carried downstream by the flow of water, and often become stuck at points where the stream bends or is unusually shallow. These areas can be especially fruitful for rock hunting after heavy rain, as the higher volume of water will cause more rocks to loosen and flow downstream.

Dig Safe Considerations

When choosing a dig site, it’s also critical to keep safety in mind. This is especially important for backyard geologists, as poorly planned digging in residential areas can cause accidental damage to pipelines and other buried utilities. Damaged utilities can be dangerous, inconvenient, and expensive to repair.

If you plan on digging more than a few inches deep in your yard, it’s essential to first identify the locations of any underground utilities on your property. You can do this by calling 811 or submitting an online request through your state’s 811 website. This preliminary step will ensure that all the buried utilities in your yard are clearly labeled on the surface, and allow you to dig without worry.

Rock Collecting

Once you understand the fundamentals of backyard geology, it’s time to start thinking about your rock collection. Rock collecting is a great way to showcase your findings and continue learning from them. Building a large rock collection can help you more easily identify new specimens by allowing you to compare them with a diverse set of samples.

How to Get Started

Even if you’re brand new to rock collecting, getting started is easier than you think. The first steps in starting any rock collection are to gather the necessary equipment and pick out a suitable dig site on your property. Once you’ve done both of these, you can start looking for specimens and classifying them using the methods discussed above. Every time you add a rock to your collection, it’s important to record what you’ve found, either in writing or on a computer. This will help you keep your collection organized and remember what you learn.

Storing Your Rock Collection

As you begin accumulating a collection of rocks, it’s critical to think about how you’re storing them. Rocks that aren’t properly stored can become lost, damaged, or worn down, compromising their value and your ability to enjoy them. The two main things to consider when storing your rock collection are protection and labeling.

To keep it protected, your rock collection should be stored in durable containers that can be securely closed. Clear containers with multiple compartments are ideal for organization and accessibility. It is also important to make sure your rocks are all clearly labeled. You can do this by using adhesive labels or by creating a written chart that corresponds with how the collection is organized.

Geological Considerations for Buyers and Homeowners

In addition to being fun and a rewarding hobby, backyard geology can also provide you with useful information that you can use to guide key real estate decisions. When you’re deciding whether to buy or sell a property, considering the geological factors can help ensure that you make the safest and most financially prudent choice possible. There are several geological considerations that you can use to evaluate risk when buying or selling a home:

  • Seismic Activity: Seismic activity or earthquakes can cause significant damage and even destroy a home completely. Before you buy a home in a new city or state, be sure to look at geological factors like proximity to fault lines, deformation of local rocks, and the history of earthquakes in the area.
  • Likelihood of Landslides: Landslides are another form of natural disaster that can damage or destroy homes. A landslide occurs when gravity causes surface debris like rocks and soil to move down a slope in the earth’s surface. Checking the United States Geological Survey’s landslide hazard maps to determine the risk in your area can help you decide when to sell your home or other property.
  • Wildfire Threats: While wildfires are not typically thought of as geological events, studying geological factors like climate history and soil dryness can help us understand the risk of wildfire in a particular area.
  • Flooding Threats: Flood risk can have a major role in determining the property values in a given area. Some of the geological considerations related to flood risk include the absorption level of local soil and the permeability of rocks in nearby valleys. When excess water cannot soak into the soil or flow evenly into valleys, flooding becomes much more likely.
  • High Wind Warnings: While geology can’t help you predict when hurricanes or tornadoes will come to your area, studying the wind erosion on nearby geological features can give you a good idea of the area’s typical wind patterns, and thereby determine the risk of high-wind warnings.

Regardless of where you’re buying, geological factors can potentially affect the security and value of your home. Being aware of local geology can help you stay ahead of risk and avoid making a bad investment. If you’d like to learn more, there are numerous digital tools and online resources available for amateur geologists at all levels.

Geology Apps

Fortunately for amateur geologists, there is a wide range of apps available that make it easier to conduct research and learn new information about the field. Here are some of the most useful apps for backyard geology:

  • Google Earth: While it’s not a geology-specific app, Google Earth can be used for a range of geological purposes, such as studying different types of terrain and mapping out geological features. Available on Android and Apple devices.
  • Flyover Country: Made specifically for geologists who travel frequently, Flyover Country provides you with a virtual map of geological features and fossil locations that can be found on your planned travel route. The Flyover Country app is available on Android and Apple devices.
  • Lambert: The Lambert geocompass app turns your device into a geological compass, allowing you to measure planes, lineations, and the angle of geological strata. The Lambert app is available on Apple devices.
  • QuakeFeed: The popular earthquake-reporting app QuakeFeed provides you with a virtual map detailing the location and severity of recent earthquakes all over the world. The QuakeFeed app is available on Apple Devices.
  • Smart Geology Mineral Guide: The Smart Geology Mineral Guide app offers users a detailed mineral classification chart, a dictionary of important geology terms, and a virtual geologic time scale. This app is available on Android devices.

Geology Activities for Kids

These activities for young geology enthusiasts offer engaging lessons designed to inspire their curiosity and provide them with valuable lessons about the fundamentals of the field:

  • Crayon Rock Cycle: The crayon rock cycle involves applying heat and pressure to a pile of grated crayons to mimic the rock cycle. This activity can be done in under an hour and requires only old crayons to complete.
  • Edible Geodes: This activity entails making geode-shaped treats by melting candy and allowing it to re-harden in a different shape. Making edible geodes is fun, tasty, and can help teach children how real geodes are formed
  • Growing Salt Crystals: This activity is simple and suitable for children as young as preschool. Growing salt crystals involves filling a tray with a supersaturated saltwater solution and allowing the water to evaporate, leaving only salt crystals.
  • LEGO Layers of the Earth: For this activity, children will use different colored LEGO bricks to create a small model that showcases the layers of the earth. This activity is fun and can help children memorize the earth’s layers and their positions.

Additional Geology Resources for Home Buyers

Before you buy a home, conducting geological research and due diligence can help you stay ahead of environmental risks and minimize potential losses. Prospective home buyers can use these geology-focused resources to ensure the security and prudence of their investment:

  • USGS: The USGS (United States Geological Survey) website offers a selection of resources that home buyers can use to identify potential geological hazards. Here, you can find maps and data that describe the location and severity of earthquakes, landslides, volcanoes, and wildfires all over the world.
  • Earthquake Track: This is another site dedicated to tracking and mapping the location and size of various earthquakes around the globe.
  • NOAA: The NOAA (National Oceanic and Atmospheric Administration) website offers users an interactive map detailing the locations of various natural hazards around the world, including earthquakes, tsunami events, and volcanic eruptions.
  • NASA Earth data: NASA provides a large volume of real-time geological and natural disaster-related data gathered by its EOS (Earth Observation System). Here, you can track floods, fires, droughts, severe storms, and more.
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Last updated: 03/09/2022

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