Rocks Archives - Eva Varga

February 27, 2016

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.

Geology Rocks

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

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 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.

North-Star-GeographyDuring 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 resourcesGeology 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.


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.

Our Dynamic Earth

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!


October 2, 2014

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.

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.

typesofrocksThe 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.

typesrocksIdentifying 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.


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

February 29, 20122

The nature study we selected this week was Quartz.  Prior to undertaking the readings suggested by Barb, my little guy helped me to gather up all of our Quartz specimens or rock samples.  As he helped, he hinted that he would like a piece of Rose Quartz for his own budding collection. I was happy to oblige him.

Our quartz specimens

I read aloud from the Handbook of Nature Study while the kids made careful observations of the samples on hand. They even tested Quartz’ ability to cut glass and they were intrigued to learn that glass is in fact made of sand .. which is composed primarily of Quartz.  We were also surprised to learn that Amethyst is in fact a type of Quartz. As I read this, Buddy jumped up to retrieve his sample from his collection.  He brought back two samples … one distinctively Amethyst and another very similar only amber in color.  “Is this Quartz too?” he asked.  “I’m sure it is,” was my reply. “But to be honest, I need to do a little research myself.”

Investigating and sketching  

I encouraged the kiddos to sketch a sample or two in their journals. Not surprisingly, frustrations quickly emerged. I couldn’t help but empathize with them … I, too, feel rocks are difficult to draw. Nonetheless, everyone recorded something.

Our completed journal entries
So why are there four journals this time?  We were delighted to share this lesson with a friend of ours … she had joined us this day while her mom did her civic duty at jury selection.