Rock Cycle Archives

Geology is an earth science comprising the study of solid Earth, the rocks of which it is composed, and the processes by which they change. Often, it can also refer to the study of the solid features of any celestial body (such as the geology of our Moon or Jupiter).

The study of geology is not always easy. Admittedly, I have a hard time identifying rocks. I can generally determine to which of the three rock types the specimen my son finds on the shoreline belongs, but that is about the extent of my identification skill. It is a skill that certainly takes practice.

When teaching geology concepts, I generally focus on the processes of change like plate tectonics and erosion. I know I’m not alone so today, I share a variety of geology activities and resources that you can incorporate into your science curriculum.

Three types of rock:

Igneous rocks are formed when hot magma (melted rock) is rapidly cooled, either by hitting underground air pockets or by flowing from the mouth of a volcano as lava. Granite, obsidian, and pumice are all common examples of igneous rocks. Pumice is a very porous rock, because when the lava cooled, pockets of air were trapped inside. Because of all those air pockets, pumice can actually float!

Sedimentary rocks are formed by layers of sediment (dirt, rock particles, etc.) being mixed and compressed together for extended periods of time. Common examples of these rocks are limestone, sandstone, and shale. Sedimentary rocks often have lots of fossils in them because plants and animals get buried in the layers of sediment and turned into stone.

Metamorphic rocks are a combination of rock types, compressed together by high pressure and high heat. They usually have a more hard, grainy texture than the other two types. Schist, slate, and gneiss (pronounced like ‘nice’) are metamorphic rocks.

Geology Activities

Science Milestones

My kids love history. I thereby incorporate history of science lessons throughout our science curriculum. Through biographies and non-fiction materials, students can learn about the work of geologists and the impact they have had on our world.

For example, Alfred Wegener is best known for his theory of continental drift. Yet his impact on our understanding of geology is so much more. He was he was also the first to describe the process by which most raindrops form.

Science Careers

Learning about careers in science is another avenue by which students can learn about the work of geologists. My kids recently visited a hydrogeology office and talked with the engineers, water resource specialists, and geologists.

Orienteering

Orienteering is a family of sports that requires navigational skills using a topographical map and compass to navigate from point to point in diverse and usually unfamiliar terrain.

Field Trips & Site Visits

One of the best ways to learn about geology is through field excursions, especially when accompanied by resource specialists. Often national parks provide ranger talks on the geology of the park.

During our week in the Galapagos, our guides interpreted the geology of the archipelago on a daily basis. Seeing evidence of the geological processes we had read about in North Star Geography solidified our understanding volcanic change, erosion, succession, and plate tectonics.

Reach out to the resource specialists at local agencies like the Forest Service and National Association of Conservation Districts to see if they might be willing to guide you on a field experience.

Geology Resources

Local Clubs

Many local communities have geology clubs that provide an opportunity to connect people who love to share what they know with others. Often local clubs will have an annual show or display – perhaps at a community center or public library.

Our local club collaborates with the community college and interpretive center to offer a monthly lecture series. Topics in the past have included The Tortoise and the Hare: Slow vs. Fast Earthquakes and Parks and Plates: How Earth’s Dynamic Forces Shape our National Parks.

Their passion for mineralogy and geology is contagious. I highly recommend you take advantage of their expertise for your homeschool co-op.

If rock collecting is a hobby you enjoy, consider joining a local rock club. It is a great way to increase your knowledge and get more enjoyment from your hobby.

Curriculum

There is a wide variety of geology curriculum available, some specifically written with homeschoolers in mind. 2015 was the Year of Soils and the USDA provided a wealth of activities and lesson plans to engage students in soil ecology.

The Kansas 4-H Geology Leader Notebook is a comprehensive set of lesson plans for 4-H geology project leaders.

For hands-on geology lessons, check out Our Dynamic Earth is a 10 week hands-on earth science curriculum unit study on the geology of our Earth incorporating scientific inquiry and language arts applications. Available today!

It is not easy to tell the difference between rocks & minerals because there are so many kinds of them. It takes years of study to be able to accurately identify a mystery rock.

Last week, we learned of the rock cycle which describes the dynamic changes over time among the three main rock types: sedimentary, metamorphic, and igneous. Today, the kids took part in two rock identification labs to further develop their understanding of the basic rock types.

A mineral is a naturally-occurring substance formed through geological processes that has a characteristic chemical composition, a highly ordered atomic structure, and specific physical properties. A rock is a naturally occurring aggregate or combination of minerals. Rocks do not have a definite chemical composition. All rocks are made of 2 or more minerals, but minerals are not made of rocks.

The Three Main Rock Types

Twelve stations were set up around the room – each with a rock specimen and a card that provided hints as to how that rock was formed. The students rotated amongst the stations and recorded first the name of the rock and then identified which of the tree rock types to which it belonged.

Here are just a few examples of the text clues given on the cards:

Marble :: In the past this was a sedimentary rock called limestone. However, heat and pressure have changed it into a much harder rock called marble. Marble today is used as a building material.

Limestone :: This rock formed when the small skeletons of diatoms, plankton, and other water animals sink to the bottom and are then buried and squeezed to form rock.

Pumice :: This rock came from the foot of a small volcano in central Oregon called a pumice cone. It is so full of holes that it will float in water.

Identifying Rocks – Using a Dichotomous Key

We then utilized a dichotomous rock key to identify a dozen or so small rock and mineral samples. In most cases, we don’t see a rock during its formation, so we rely on rocks’ observable clues to infer their formations. Two clues that indicate a rock’s formation are its composition and texture.

Composition refers to what a rock is made of. The color of a rock can provide a clue to the composition. Fragments of other rocks, fossils, and identifiable mineral grains are also aspects of composition.
Texture is a description of the rock material. It includes characteristics such as crystal size and shape, number of different grain sizes, and alignment of grains.

Together we observed the rock’s texture, conducted a basic hardness test, and identified the minerals that compose it as best we could.

When Using a Rock Key there are a few things you need to know:

When minerals have the time and space to grow into their crystal forms, they grow to beautiful regular shapes that are easy to recognize once you have seen a few examples. In rocks, crystals grow up against each other; they have straight edges and often show flat shiny faces that reflect light like tiny mirrors.

Grains that are not crystals in rock do not have flat shiny faces. They are rounded, like grain of sand, or jagged, like a piece of broken rock. Grain size in rocks can mean the size of crystal grains or of fragments:

Coarse Grained – the rock is mostly made of grains as large as rice, or larger
Medium Grained – the individual grains can be seen without a magnifier, but most of the rock is made of grains smaller than rice
Fine Grained– the individual grains can not be seen without a magnifier

Layers in rocks show in different ways.

In some rocks (gneiss for example) different colored minerals are lined up in ribbons.
In schists, the layers are most often thin layers of mica or chlorite around masses of feldspar or quartz. The top and bottom is almost always mica or chlorite.
In sandstones, different sized sand grains sometimes show as different colors. When the grains are sorted by running water or wind, they show different shades of the same color.
The layers in slate are very thin and straight. The top and bottom layers are usually flat and quite smooth.

Gas bubbles form round or elongated holes in rocks. In pumice, the bubbles may be very tiny. In scoria or vesicular basalt, the bubbles are larger, often as large as peas.

rocktypes

For more information on rock types and identifying rocks, I recommend these resources:

The Rock Identification Key – An online, interactive dichotomous key that walks you through precise steps (no photos)
Identification of Minerals – This website provides clear definitions for common terms or characteristics used to id rocks (cleavage, luster, specific gravity, streak, fracture, etc.)
Rock Identification Tables – A website to help you identify rocks (the tables are clear and provide full color photographs of many rock samples)
Simon & Schuster’s Guide to Rocks & Minerals – An easy to use field guide that contains everything rock and mineral enthusiasts need to know, +1,000 spectacular illustrations
Smithsonian Rocks & Minerals Handbook – Another great field guide that combines 600 vivid photos with descriptions of more than 500 specimens.

Rocks, like mountains, do not last forever. The weather, running water, and ice wear them down. All kinds of rocks become sediment. Sediment is sand, silt, or clay. As the sediment is buried it is compressed and material dissolved in water cements it together to make it into sedimentary rock. If a great amount of pressure is exerted on the sedimentary rock, or it is heated, it may turn into a metamorphic rock. If rocks are buried deep enough, they melt. When the rock material is molten, it is called a magma. If the magma moves upward toward the surface it cools and crystallizes to form igneous rocks. This whole process is called the Rock Cycle.

In STEM Club this week, I shared a game with the students with which we simulated cycling through the rock cycle. I began the lesson with a visual diagram of the rock cycle laid upon the tables and requested the students copy it into their journals. The three major rock types (igneous, metamorphic, and sedimentary) were illustrated, as well as the processes that act upon the rock material.

rockcycle

Magma is molten rock. Igneous rocks form when magma solidifies. If the magma is brought to the surface by a volcanic eruption, it may solidify into an extrusive igneous rock. Magma may also solidify very slowly beneath the surface. The resulting intrusive igneous rock may be exposed later after uplift and erosion remove the overlying rock. The igneous rock, may then undergo weathering and erosion and the debris produced is transported and ultimately deposited (usually on a sea floor) as sediment.

If the unconsolidated sediment becomes lithified (cemented or consolidated into rock), it becomes a sedimentary rock. As the rock is buried the additional layers of sediment and sedimentary rock build and thereby heat and pressure increase. Tectonic forces may also increase the temperature and pressure. If the temperature and pressure become high enough, usually at depths greater than several kilometers below the surface, the original sedimentary rock is no longer in equilibrium and recrystallizes.

The new rock that forms is called a metamorphic rock. If the temperature gets very high the rock melts and becomes magma again, completing the cycle. The cycle can be repeated, as implied by the arrows. However, there is no reason to expect all rocks to go through each step in the cycle. For instance, sedimentary rocks might be uplifted and exposed to weathering, creating new sediment.

Rock Cycle Game

Set up eight stations at which a change in the rock cycle occurs:

Earth’s Interior
Soil
River
Ocean
Clouds
Mountains
Volcano

Each student starts at one area. At each area is a die that the student should role to determine what path they should take. It is possible for the student to remain at the same station for a long time. To alleviate frustration, I thereby stated that after 3 turns the student could go to another station.

While at each station and while moving to the different stations, students must record what is happening. For example,

“I began my adventure at ________ . The first thing that happened was _________, then I went to ___________.”

Students continued to work through the rock cycle for several minutes (until the majority had cycled through 12 steps).

Cartoons

After their journey through the rock cycle is complete, students are encouraged to create a cartoon describing their adventures in the rock cycle. Each cartoon page should be divided so there are 12 boxes (one for each ‘step’ in the rock cycle).

Try it yourself! Download the student handouts and station cards .. Rock Cycle Journey.

Rock Cycle Archives - Eva Varga

Geology Rocks! Activities and resources to enhance your geology lessons