Guided Exploration: How Earth Formed




1. Meteorites (#1–3)

The most important clues to the composition of the early solar system come from meteorites. Observe these three and explore the evidence about Earth’s formation that they contain.

Iron Meteorite

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Iron meteorite

A third relic of the ancient cosmos is this iron meteorite, Mungindi.

2. Four Density Blocks (#4-7)

When Earth was forming, heavier materials like iron sank to the center to form the core and lighter ones like silicates rose to the surface. Lift the four samples and compare their weights. How does this connect to how Earth’s layers are organized?

Earth's Layers: Core

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Core (Iron)

The Earth’s core, its densest layer, is made up of iron-nickel alloy.


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Mantle (Peridotite)

Peridotite, a rock made up primarily of the minerals olivine and pyroxene, is the chief constituent of the Earth’s upper mantle.

Earth's Layers: Crust

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Crust (Granite)

Granite, an igneous rock composed mainly of the minerals quartz and feldspar, makes up most of the upper crust.

Earth Layers: Ocean

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Oceans (Water)

As the Earth’s surface cooled below 100 degrees Centigrade, water rained out of the atmosphere to form the ocean.

3. Banded Iron (#23, 15) and Stromatolite (#14)

Rocks can contain important clues about the atmosphere. In early Earth, metals like iron were released into the ocean from hot springs but remained in solution in the water. When photosynthetic organisms began producing oxygen, it reacted with the iron in the seawater and precipitated as iron oxide to form the banded iron formation. Eventually, oxygen began to accumulate in the atmosphere. Observe both banded iron formations and the stromatolite (the fossilized remains of early oxygen-producing microbes). Then, look at the “How Do We Know About the Early Atmosphere?” diagram to explore the way these two rocks formed and what this tells us about the early atmosphere.


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Banded Iron Formation

A nearly 3-billion-year-old banded iron formation from Canada shows that the atmosphere and ocean once had no oxygen. 

Ontario Banded Iron Formation

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Ontario banded iron formation

This banded iron formation comes from a rock unit 60 meters thick that formed over a 50-million-year period, from 2.736 to 2.687 billion years ago.

A Stromatolite From Mauritania

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A stromatolite from Mauritania

An entire colony of microbes piled on one another over time, forming semi-rigid, upward-pointing, and branching columns mirrored in this 900-million-year-old stromatolite.

4. Sulfide Chimneys and Banded Ore (#26)

Chimneys form today when iron and other metals from underwater hot springs react with seawater and precipitate, in this case as sulfide minerals. Walk past the Dynamic Earth Sphere to observe the chimneys at the other end of the hall. Examine the “Deep-Sea Vents and Ore Deposits” panel to find out how these two very different ore deposits formed.


Chimney Roane

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The Chimney Roane

Roane contains a complex series of interconnected channels and isolated voids. 

Chimney Gwenen

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The Chimney Gwenen

These are two halves of the top of Gwenen, a five story-high spire that was venting water at 179 degrees Centigrade.

Banded ore_HERO

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Banded ore

The ore body is composed mainly of zinc and copper-iron sulfide minerals.