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Earth and Space 6-8 / Week 09 / Friday
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Week 09 · Rocks Change

Friday

Rocks in the real world
// Energy flows, matter cycles, rocks turn into other rocks
⏱ about 20 min

Friday: Rocks in the Real World

Rocket arrives at the Sky Deck with a photo of a huge granite dome. "This was underground," he says. "Thousands of feet underground."

Raven reads the caption. "Half Dome, in a California valley. Now nearly 8,800 feet above sea level."

"So the crust lifted it and the rock on top wore away," Rocket says. "The cycle, but for real."

Nova hovers over the photo. "The survey also describes limestone in Texas that was a coral reef," she says. "About 250 million years ago."

"What do you notice?" Raven asks. "Every famous rock is partway around the loop."

Rocket laughs. "So is our gravel path." Nova hums. "Now you see rocks the way geologists do."

Rocks tell the story of the Earth

The survey describes the Guadalupe Mountains of western Texas. There you can stand on limestone that was a coral reef in a tropical sea about 250 million years ago.

In Vermont's Green Mountains you can see schist, a metamorphic rock, that was once mud in a shallow sea.

Half Dome in Yosemite Valley stands nearly 8,800 feet above sea level. It is made of an igneous rock that solidified several thousand feet within the Earth.

Rock-forming and rock-changing processes have been active for billions of years. A small collection can capture an enormous sweep of Earth's history.

Place from the surveyRock nowGroupWhat it used to be
Guadalupe Mountains, Texaslimestonesedimentarya coral reef in a tropical sea, about 250 million years ago
Green Mountains, Vermontschistmetamorphicmud in a shallow sea
Half Dome, Yosemite Valleyan igneous rockigneousmelt that hardened several thousand feet underground
PARTWAY AROUND THE LOOP
  • Read the question.
  • Tap your answer.
Which process lifted Half Dome's rock from thousands of feet underground to 8,800 feet above sea level?
The Vermont schist began as mud. Which two things changed it into metamorphic rock?
A coral reef becoming limestone is an example of which part of the cycle?
Week reviewTrue or false?
Igneous rock forms from melted rock that cooled and hardened.?
Sedimentary rock forms in layers at the surface.?
Metamorphic rock forms when heat and pressure change an older rock without melting it.?
The rock cycle has one engine: the Sun.?
A rock walk can suggest a group but cannot prove it.?
WHY THIS EXERCISEThese ideas are the whole week: three groups, two engines, one cycle, and honest evidence.
OUR WEEK, IN ORDER
  • ?We met three rock groups sorted by how they formed.
  • ?We read the survey's descriptions as a data table.
  • ?We traced the rock cycle and its two energy engines.
  • ?We sorted loose rocks and built a card model of the cycle.
  • ?We found the cycle in mountains, reefs and a granite dome.
WHY THIS EXERCISEThe week moved from a handful of rocks to a model you can explain.
Which group is the Guadalupe Mountains limestone? Type one word.
WHY THIS EXERCISELimestone shows that living things can become rock too.
Try it
Walk your block or hallway and find three rock-like materials: brick, concrete, gravel, a stone step or a countertop.
For each, say which rock group it most resembles and why. Write the best one in your Sky Log.
Draw Half Dome twice: once as melt deep underground, once as the dome today. Show the worn-away rock as a dotted outline.

Strong week, geologist. Tomorrow is Sky Night: a family rock walk, a Moon check and a cloudy-night backup.

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