Guided Exploration: Plate Tectonics

 

HoPE Tour Map: Plate Tectonics

 

What is Plate Tectonics? 

1. Bronze Globe 

Observe this model to explore the solid Earth — what the Earth looks like without water. (To understand the term “solid Earth,” watch the Dynamic Earth sphere overhead and see the liquid slowly drained away from the rocky surface). Compare the familiar topography of the continents with the less familiar topography of the ocean basins. Then look at the “slice of crust” model hanging overhead. Use the diagram below to find the region on the globe that’s represented in the model above. In this part of the hall, you’ll be exploring the ways in which plate tectonics shapes the solid Earth.


2. Churning Earth Section

Convection is the main way in which heat is lost from the interior of the Earth. It’s the force that drives the movement of tectonic plates. Go to the video kiosk in the circular table and watch scientific models of how the Earth’s core and mantle convect.

The Churning Earth

Hall Section

The churning Earth

The mantle is mostly solid rock, but because it is hot, it flows in slow, circulating patterns.



 

When Plates Collide

3. Model of Collision

When an oceanic plate meets a continental plate, the oceanic plate descends, or subducts, beneath the continental plate and sinks into the mantle. Explore the model and use your hands to simulate how plates collide.

Plate Colliding Model

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Where plates collide

The most geologically active regions on Earth are where plates collide.


4. Explosive Volcanism Section

Explore why most explosive eruptions occur in volcanoes above subduction zones. Examine samples from Medicine Lake Volcano, California (#5-10), and watch a video of scientists at work in Indonesia.

Subduction Zone Volcanism

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Explosive volcanism

Most explosive eruptions occur in volcanoes above subduction zones, where one tectonic plate dives beneath the other.



Basalt Tablet

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Basalt tablet

The composition of the magma that formed this tablet was basically unchanged by its journey from the mantle to the surface, where it erupted to form a smooth, sinuous lava flow.



Pumice

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Pumice

This pumice has the same composition as the obsidian next to it.


Obsidian

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Obsidian

Obsidian is a volcanic glass, a comparatively rare and crystal-poor form of rhyolite, the most silica-rich lava.


Remnants of a Buried Forest

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Remnants of a buried forest

Glass Mountain began with an explosive eruption of ash that blanketed the surrounding forest, killing all the trees.



5. Mountain Formation Section

When two continental plates meet, one is thrust over the other to form mountain ranges like the Alps and the Himalayas. Watch the video and examine the sand model, and think about how the model helps scientists understand the way plates interact to form mountain ranges. Then observe the rock samples (#1-7) that illustrate the processes (uplifting, folding, crustal thickening, and faulting).

How Mountains are Formed

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Mountain building

The mountain ranges that span the globe mark boundaries where the Earth’s plates converge.


Modeling Mountain Building

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Modeling mountain building

Physical models can provide insight into how the deep structures - the folds and faults - of mountain belts actually form.



Barrovian Sequence

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Barrovian sequence

These four samples were originally identical shales whose mineralogy changed as they were subjected to increasing pressure and temperature.


Ultra-High Pressure Rock

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Ultra-high pressure rock

The presence of diamond in this rock indicates that it had been buried to a depth of about 130 kilometers.


Gore Mountain Garnet

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Gore Mountain garnet

This sample of garnet-bearing amphibolite is a spectacular illustration of how metamorphism and deformation can cause a complete change in texture.


Eclogite

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Eclogite

From the core of the Alps, this eclogite represents a sliver of oceanic crust that became trapped and caught up in the continental collision that formed the Alps.


A Fold in a Rock-Schist

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A fold in a rock

This rock illustrates how seemingly brittle material can flow, given enough time and heat.


Deformed Conglomerate (Hemlo Greenstone)

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Deformed conglomerates

These rocks were originally deposited in a stream as layers of rounded pebbles.



When Plates Move Past Each Other

6. Model of Slip

A fault forms when oceanic or continental plates slide past each other in opposite directions, or move in the same direction but at different speeds. Explore the model and use your hands to simulate how plates move past each other.

When Plates Move Past Each Other

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When plates move past each other

When oceanic or continental plates slide past each other in opposite directions, or move in the same direction but at different speeds, a transform fault boundary is formed.


7. Earthquakes Section

Earthquakes occur along fault lines (cracks near plate boundaries where the crust on opposites sides moves). Explore the earthquake video kiosk and associated text panels to find out how monitoring helps scientists estimate the odds of an earthquake taking place within a certain period of time. Then find the faults on the two large casts and the samples (#1-2) and examine what they tell us.

Earthquakes

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Earthquakes

No other natural force compares in sheer power with earthquakes.



Which Way Does a Fault Move?

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Which way does a fault move?

Slickensides are grooves and steps created on a fault surface by the slow, grinding movement of two bodies of rock against each other.


When Plates Separate

8. Model of Separation

Most spreading plate boundaries are found in ocean basins. Explore the model and use your hands to simulate how plates separate.


9. Basalts

Most volcanoes erupt basalt, a fluid lava from the mantle that forms flows. Most basalt erupts from cracks in the seafloor, but some basaltic lava flows occur on continental crust. Compare the shapes of the underwater (#9-17) and flood basalts (#18), and explore their formation.

Glassy Buds

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Glassy buds

These pillow buds from the East Pacific Rise formed when the magmatic pressure within a pillow caused tiny fractures through which magma seeped.


East Pacific Rise Pillow Basalt

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East Pacific Rise pillow basalt

The reddish rind on this pillow is made of palagonite, a clay-rich layer that formed when pillow’s hot exterior reacted with cold seawater.


Lava Pillars

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Lava pillars

These pillars were collected on the East Pacific Rise. 





Pacific Ocean Pillow Basalt

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Pacific Ocean pillow basalt

The glassy crust has broken off the rounded surface of this pillow, exposing the dark, fine-grained basalt beneath.


East Pacific Rise Pillow Basalt

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East Pacific Rise pillow basalt

The reddish rind on this pillow is made of palagonite, a clay-rich layer that formed when pillow’s hot exterior reacted with cold seawater.



When Plates Move

10. Hawaiian Hot Spots

Basaltic lava also erupts at hot spots, where molten rock, or magma, forms in plumes of hot rock that rise from deep in Earth to penetrate a moving plate above. Watch the video and explore the various specimens. What does the pattern of the Hawaiian island chain reveal about how the Pacific plate is moving?

The Hawaiian hot spot

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The Hawaiian hot spot

A chain of 107 volcanoes – some islands, some submerged – extends from Hawaii to the northwest.


Wrap Up

11. Bronze Globe: Revisit the globe and connect specific specimens to places on the globe and to the tectonic processes at work behind them. (Examples: Collide — Andes and Himalayas; Separate — Mid-Atlantic Ridge; Slip — San Andreas fault)