Week 1: Rock Types & the Rock Cycle

Grade 7 Science | Rosche

MS-ESS2-1 Earth's Systems

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The Phenomenon: The Mountaintop Seashell Mystery

Anchoring Context & Focus Question

How can you find seashells on top of a mountain?

Diagram of the rock cycle showing igneous, sedimentary, and metamorphic rocks at the corners of a triangle, connected by the processes of weathering and erosion, heat and pressure, melting and cooling, and uplift
Rock cycle diagram. Review once before beginning the station activities.
Animated explanation of the week's focus question. Watch then reason about why this happens.
Key Vocabulary (6 terms) — Practice Tool

Cognate Strategy: Many science words look similar in English and Spanish — use your Spanish to learn science!

Term Spanish Definition
igneous rock roca ígnea Rock formed from cooled magma or lava
sedimentary rock roca sedimentaria Rock formed from compressed layers of sediment
metamorphic rock roca metamórfica Rock changed by heat and pressure
rock cycle ciclo de rocas Continuous process of rock formation and transformation
weathering meteorización Breaking down of rocks by wind, water, ice, and living things
uplift levantamiento The rising of Earth's crust, often due to plate tectonic forces, exposing buried rocks

Hook – The Mountaintop Seashell Mystery

Examine fossil evidence from mountain peaks and generate hypotheses about how ocean organisms ended up at high elevations.

The Mountaintop Seashell Mystery

Scientists climbing Mount Everest found marine fossils (trilobites, brachiopods, crinoids) embedded in limestone — 29,000 feet above sea level. These organisms lived in an ancient ocean over 450 million years ago. How did creatures from the sea end up on top of the world's tallest mountain?

Diagram of Mt. Everest's snow-capped summit at 29,000 feet with a callout enlarging the trilobite, brachiopod, and crinoid marine fossils preserved in its summit limestone.
Marine fossils sitting 5.5 miles above sea level — the puzzle this week solves.

Cycle 6 Connection

Use what you learned about plate tectonics: convergent boundaries push crust upward to form mountains. But the fossils are in sedimentary rock — what does that tell you about how this rock formed, and what had to happen to bring it so high?

What You'll Do

  1. Examine fossil and rock evidence from the Himalayas
  2. Retrieve what you already know about plate tectonics (Cycle 6)
  3. Predict how three rock types might be connected
  4. Submit your reasoning — no wrong answers yet, just your best thinking
COMPLETE THE HOOK FORM

Analyze fossil images from the Himalayas and make predictions about rock formation.

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Worked Example – Classifying Rocks by Formation Process

Worked Example: Classifying Rocks by Formation Process

Problem: A geologist gives you three hand samples — a rock with visible crystal grains, a rock with stacked sandy layers and a fossil, and a rock with wavy banded stripes. She asks: "Which is igneous, sedimentary, or metamorphic — and how do you know?"

Three rock hand samples with diagnostic clues: interlocking crystals for igneous, layers plus a fossil for sedimentary, and wavy bands for metamorphic.
Use texture as evidence: crystals, layers, fossils, and bands point to formation process.

Step 1: Look for Formation Clues

  1. Crystals interlocked (no layers, no fossils) → cooled from melt → IGNEOUS
  2. Layers + particles + fossils → deposited and compressed → SEDIMENTARY
  3. Bands, foliation, or stretched minerals → heat + pressure changed it → METAMORPHIC

Step 2: Connect to the Rock Cycle

Every rock can become any other rock. Weathering + deposition + compression turns igneous into sedimentary. Heat + pressure turns sedimentary into metamorphic. Melting turns any rock into magma — and the cycle starts over. There is no "end" to the cycle.
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Station 1 – Rock Classification Lab

Classify rocks by formation process and identify igneous, sedimentary, and metamorphic types.

Station 1 — Rock Classification Lab

Your mission: classify 8 rock samples using the observation → inference → formation process workflow you saw in the worked example. You'll use texture, mineral composition, and structural clues (layers, bands, crystals) to place each sample in the correct rock-cycle family.

Evidence Checklist

For each sample, record: (1) visible grain size, (2) layering or banding pattern, (3) presence of fossils or gas bubbles, and (4) your best-supported claim about formation process.
Three labeled rock samples showing the diagnostic clues to look for: interlocked crystals (igneous), horizontal layers with a fossil (sedimentary), and folded bands (metamorphic foliation).
Reference card: what each rock type "looks like" under your magnifier.
COMPLETE THE STATION 1 FORM

Classify rock samples and identify their formation processes.

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Station 2 – Rock Cycle Modeling

Model transformations between rock types through the rock cycle.

Station 2 — Tracing Materials Through the Rock Cycle

Follow a single calcium carbonate molecule on a 200-million-year journey: from a shell in a shallow sea → limestone on the ocean floor → marble in a mountain range → sand in a river → back to a reef. You'll use a rock-cycle diagram to predict each transformation and the process that drives it.

Processes to Track

  1. Weathering/erosion — breaks rock into sediment
  2. Deposition + compaction + cementation — forms sedimentary rock
  3. Heat + pressure — metamorphism (no melting!)
  4. Melting + cooling — creates new igneous rock
Five-stage diagram of one calcium carbonate molecule's 200-million-year journey: shell in shallow sea, limestone on the seafloor, marble in a mountain range, sand in a river, and back to a coral reef.
Same atoms, different rocks: track CaCO₃ across all four rock-cycle processes.
COMPLETE THE STATION 2 FORM

Model and explain how rocks transform from one type to another.

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Station 3 – Design a Rock Formation Timeline

Apply rock cycle understanding to create explanations for formation sequences.

Station 3 — Evidence of the Rock Cycle in Missouri

The St. Louis area sits on 340-million-year-old limestone from an ancient inland sea. The Ozark Mountains to the southwest show rhyolite (igneous) and metamorphic rocks from even older events. Your task: use USGS data and rock samples to reconstruct Missouri's rock-cycle history.

Local Evidence to Analyze

  1. St. Louis limestone bluffs — sedimentary evidence of the Paleozoic sea
  2. Taum Sauk Mountain rhyolite — 1.5-billion-year-old volcanic rock
  3. New Madrid seismic zone — ongoing tectonic activity that could recycle today's rock
Stylized map of Missouri marking the three rock-cycle evidence sites: St. Louis limestone bluffs (NE), Taum Sauk Mountain rhyolite (SE), and the New Madrid seismic zone (bootheel).
Three sites, three rock types, 1.5 billion years of cycling — all in your home state.

Argument from Evidence

Write a CER (Claim–Evidence–Reasoning) response: "What does the rock record of Missouri tell us about the rock cycle over the last billion years?" Use at least two pieces of specific evidence.
COMPLETE THE STATION 3 FORM

Design and sequence a timeline of rock formation processes.

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Exit Ticket – Rock Cycle Integration

Synthesize learning about rock types and the rock cycle.

Exit Ticket — Rock Cycle Mastery

Demonstrate your understanding of the rock cycle through 2 new-content questions, 2 spiral questions from Cycle 6 (plate tectonics drives the rock cycle!), and 1 integration question that connects rocks, plates, and the SEP practice of constructing explanations.

Exit-ticket synthesis map linking rock type evidence, rock cycle processes, plate tectonics, and the claim that ancient seafloor can become a mountain.
Exit-ticket roadmap: evidence plus rock-cycle processes plus tectonic uplift.
COMPLETE THE EXIT TICKET

Demonstrate mastery of rock cycle concepts.

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Enrichment & Extension
Optional content if you finish early or want to go deeper.

Scientist Spotlight: Marie Tharp

Marie Tharp (1920–2006) was an American oceanographer and geologist who spent 18 years hand-drafting the first detailed map of the Atlantic Ocean floor. At a time when women were barred from research ships, Tharp worked from sonar depth readings in a lab at Columbia University. Her map revealed a mid-ocean ridge with a deep central rift valley running the length of the Atlantic — direct evidence that the seafloor was spreading and continents were moving. Her discovery proved the theory of plate tectonics and helps us explain today's phenomenon: seashells end up on mountaintops because ancient seafloor gets pushed upward when tectonic plates collide over millions of years. Rocks you hike across in the Rockies or Appalachians were once buried under an ocean.

Cross-section of the Atlantic Ocean floor showing North America and Africa on either side, the mid-ocean ridge in the center, and a deep rift valley splitting the ridge — the bathymetric pattern Marie Tharp mapped to prove seafloor spreading.
Tharp's bathymetric profile: ridge + central rift valley + spreading direction.

Environmental Justice: Coldwater Creek, St. Louis

The rock cycle carries more than minerals — it also moves radioactive isotopes through sediment, water, and soil. During World War II, Mallinckrodt Chemical processed uranium ore in north St. Louis to build the first atomic bombs. Radioactive waste was stored in barrels near the airport and leaked into Coldwater Creek, which flows through predominantly Black and working-class neighborhoods in Florissant, Hazelwood, and Berkeley. Decades of flooding carried contaminated sediment into yards, schools, and playgrounds. Residents who grew up along the creek now have unusually high rates of rare cancers. Scientists studying sedimentary rock layers and soil samples are mapping where the contamination traveled — the same weathering and deposition processes you're learning this week are what spread the harm, and what cleanup crews now race to reverse.

Schematic showing radioactive uranium drums stored near St. Louis Lambert Airport, weathering and runoff carrying contaminated sediment into Coldwater Creek, and downstream deposition into the Florissant, Hazelwood, and Berkeley neighborhoods.
Same weathering + deposition processes — applied to environmental harm.
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Week 1 Complete!

Next Week: Geologic Time & Fossil Evidence — how do we know what Earth looked like millions of years ago?