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The Story of Rocks
What can a rock tell us about the history of Earth?

Rocks aren't just hard, boring objects, they're time machines that tell the story of Earth's past. In this lesson, your learner will discover that rocks come in three different types, each with its own origin story. By understanding how rocks form and change, your learner can read the landscape like a book, learning how mountains rose, how oceans covered the land, and how the Earth is constantly recycling itself.

S2S_Lesson06_FROM_LAVA_TO_LAYERS_THE_STORY_OF_ROCKS.pptx by Selene

Key Ideas

  • Igneous rocks form from cooling lava or magma.
  • Sedimentary rocks form from layers of sediments compacted over time.
  • Metamorphic rocks form when heat and pressure change existing rocks.
  • The rock cycle shows how rocks change forms over time.
  • Erosion and sedimentation continually reshape Earth's surface.

Spines
  • DK's Science as You've Never Seen it Before: pg. 22-23
  • Mammoth Science: Rocks pg. 138
✏️  Notebooking Activity
Label the diagram to show a sample rock cycle. Include the three main types of rocks (Igneous, Sedimentary, and Metamorphic) and how they interact. Identify the process required for the change (e.g., “Heat and Pressure,” “Melting,” or “Weathering and Compaction”).

Cosmic CalendarWhere we are: Mid-to-Late September*
We remain in September. The asterisk indicates this is a reasoned estimate based on the known geological timeline, not a single verified date. Read the script below before the lesson.

Read aloud:We’re staying in September on our Cosmic Calendar today. Earth has just formed, and right now the planet is a very different place from the one we know. The rocks forming in this period are recording the earliest chapters of Earth’s history. Some of the oldest rocks we’ve ever found were laid down right around this time in our calendar, in real years between about 4.4 and 4 billion years ago. We’re still early in September on the calendar. Things are moving quickly in cosmic terms, even if each step feels enormous to us. Keep watching this calendar as we go, because things are about to get very interesting.
Timeline PageLabel the next page in your timeline “From Lava to Layers: The Story of Rocks.” The workbook prompt asks learners to draw sedimentary layers stacking up at a riverbed and a metamorphic rock being squeezed deep underground.

Discussion Questions
  1. What are the three types of rocks? 
    Sample answer: Igneous, sedimentary, and metamorphic.
  2. Where do igneous rocks come from? 
    Sample answer: They form when hot melted rock called magma or lava cools and hardens.
  3. How are sedimentary rocks made? 
    Sample answer: Layers of sediment, like sand, mud, and tiny shells, get pressed together over a very long time.
  4. What conditions create metamorphic rocks? 
    Sample answer: Extreme heat and pressure deep underground change the minerals in existing rocks without melting them—the result is a denser, recrystallized rock.

Digging Deeper
  1. How does the rock cycle show that rocks are always changing? 
    Sample answer: Heat, pressure, and weathering can change any type of rock into another type over millions of years, it's a slow, continuous cycle.
  2. Why do sedimentary rocks often contain fossils? 
    Sample answer: When organisms die near water, they can get buried quickly by layers of sediment before decomposing, leaving behind impressions or bones.

SCIENTIST SPOTLIGHT: Florence BascomFlorence Bascom was an American geologist who became the first woman to earn a PhD in geology in the United States and the first woman hired by the US Geological Survey. She studied rock formations in the Appalachian Mountains and trained an entire generation of women geologists at a time when women were actively discouraged from entering science. When she applied to Johns Hopkins University, they admitted her on the condition that she sit behind a screen so the male students would not be distracted by her presence. She went on to become one of the most respected geologists of her era and is sometimes called the founder of American women in geology.

Videos:
Biography of Florence Bascom
Florence Bascom—1st American Female Geologist (1862–1945)

Books:
Digging Deeper Activity:
Bascom studied how rocks in the Appalachian Mountains formed under enormous heat and pressure. These are metamorphic rocks. Find a rock outside and try to figure out what type it is. What does its texture and appearance tell you about how it might have formed?

Vocabulary
  • Igneous Rock — Rock formed when magma or lava cools and solidifies; examples include granite (underground) and basalt (from lava at the surface).
  • Sedimentary Rock — Rock formed when layers of sediment (sand, mud, shells, or other particles) are compressed and cemented together over time; often contains fossils.
  • Metamorphic Rock — Rock changed by extreme heat and pressure deep underground, altering its mineral structure without melting it.
  • Rock Cycle — The slow, ongoing process by which rocks are created, broken down, and transformed from one type into another over millions of years.
  • Erosion — The wearing away and movement of rock and soil by wind, water, ice, or gravity.
  • Mineral — A naturally occurring, non-living solid with a specific chemical makeup; rocks are made of one or more minerals.
  • Fossil — The preserved remains or traces of ancient life found in sedimentary rock.

Sources

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