Mountain Building Using a sandbox to Model mountain building and Faults Using a sandbox to Model mountain building and Faults

Part 1 SOAR-High Collaborators

Dr. Michele Cooke Dr. Mario Del Castello Department of Geosciences, University of Massachusetts

Part 2 Structure of the Earth

The Earth  Crust  Continents  Ocean Floor  Core  Lithosphere  aethenosphere  Crust  Continents  Ocean Floor  Core  Lithosphere  aethenosphere

Earth’s Crust is made of plates  A plate is a large rigid slab of solid rock  Plates are15 km thick under the oceans  200+ thick under the continents  The Plates are Billion years old  Largest plates are under the Pacific ocean, and Antarctica.

Plates

Earth’s Crust  The plates are cracked  The cracks are called faults  The edge of a plate is called a boundary  The plates are cracked  The cracks are called faults  The edge of a plate is called a boundary

Earth’s crust  The plates are always in motion!  Changes require much more time than humans can live!  The plates are always in motion!  Changes require much more time than humans can live!  Fastest movement is 2 to 3 cm/yr  Most geologic changes require a 100 million years.  Humans live 80 years

Part 3 Kinds of Faults

Faults can be large and small  A Large scale fault  Small scale faults The San Andreas Fault in California stretches 1000 km!

Three Kinds of Faults

Part 4 The plates have moved!

The Theory of Plate Tectonics assumes that Continental Drift has occurred over millions of years.

Two kinds of movement  Extension  Pull apart force is called TENSION  Creates a RIFT  Extension  Pull apart force is called TENSION  Creates a RIFT  Contraction ===> <===  Push together force is called SHORTENING  Creates a SUBDUCTION

Extension Contraction  Drawing of extension situation  Drawing of contraction  situation

Rifts vs Subduction ( Extension )  Plates are Stretching  Involves an extensional fault ( Extension )  Plates are Stretching  Involves an extensional fault ( Contraction)  Plates are Colliding ==> <==  Involves a thrust fault Review the vocabulary

Part 5 studying mountains

Let’s study mountains!  Go out for a hike + You can see the real thing + Can make measurements & drawings -- You can’t see underground -- can’t change anything!  Go out for a hike + You can see the real thing + Can make measurements & drawings -- You can’t see underground -- can’t change anything!

Or we can Make a model  Advantages of a Model…. + you can test variables (different situations) + you can measure and draw + you can see underground (cross sections)  But … -- Is it really the same ? -- Do real mountains follow the same patterns?  Advantages of a Model…. + you can test variables (different situations) + you can measure and draw + you can see underground (cross sections)  But … -- Is it really the same ? -- Do real mountains follow the same patterns?

The Sandbox is a model of mountains  Mountains are LARGE scale.  Sand is very small scale. 1 cm deep sand = 1 km of crust  Mountains are LARGE scale.  Sand is very small scale. 1 cm deep sand = 1 km of crust

What we can measure  Strike: a fault’s orientation (north/south, east/west, or parallel, or whatever to tell how it looks.)  Dip: How steep or shallow the fault is; its angle.  Strike: a fault’s orientation (north/south, east/west, or parallel, or whatever to tell how it looks.)  Dip: How steep or shallow the fault is; its angle.

Part 6 Set up the Sandbox Go set up your sandbox now. Carefully observe what happens in the sandbox. Make small sketches of the results frequently (pause the slides here and experiment with the sandbox.

Part 7 Thinking and Understanding

Synthesis Label your sandbox drawings - Show your understanding  Label as many faults as you can  Is it an extensional or thrust fault?  Show the direction of the force.  Is the force Tension or Shortening?  What is the Dip? Measure the angles  Label as many faults as you can  Is it an extensional or thrust fault?  Show the direction of the force.  Is the force Tension or Shortening?  What is the Dip? Measure the angles

Synthesis The big picture View the sandbox from above, looking down. Make a sketch.  Draw the ‘plate’ (use the whole sand area)  Label the boundary (the edges of the sand area)  show the strike of the fault or faults  How does the surface look? View the sandbox from above, looking down. Make a sketch.  Draw the ‘plate’ (use the whole sand area)  Label the boundary (the edges of the sand area)  show the strike of the fault or faults  How does the surface look?

Part 8 Compare with the real world

Young mountains Old mountains Back in the real world - How do mountains look?

Synthesis What do you see in the real world?  How does the surface look after millions of years?  How did it change? Erosion by wind Erosion by water Erosion by temperature changes  How does the surface look after millions of years?  How did it change? Erosion by wind Erosion by water Erosion by temperature changes

 More mountain pictures…. Identify types of faults? Old/new, & other vocabulary.

Web sites  /earth/birthmountains.html /earth/birthmountains.html  /structure/block3.htm /structure/block3.htm  thcrust.htm thcrust.htm  sum.html?tname=17701&url=17701/high/ pangaea/ sum.html?tname=17701&url=17701/high/ pangaea/  /earth/birthmountains.html /earth/birthmountains.html  /structure/block3.htm /structure/block3.htm  thcrust.htm thcrust.htm  sum.html?tname=17701&url=17701/high/ pangaea/ sum.html?tname=17701&url=17701/high/ pangaea/