1. Mountain Building
Earth Science Ch. 11

2. 11.1 Forces in Earth’s Crust
Deformation: permanent change in the size or shape of rock
Occur along plate margins and in the Earth’s crust.
Stress: force applied to a rock
Strain: change in the shape of rock
Folding: bending due to gradual stress on rock
Fracturing: breaking of rock.

3. At the surface Inside the earth Temperature and pressure are low
Rocks fold and fracture
Inside the earth
Temperature and pressure are high
Folding and fracturing do not occur

4. Rock type can also affect deformation
Igneous rock is more likely to fracture than sedimentary or metamorphic rock.
Sedimentary and metamorphic are more likely to fold before they will fracture.

5. Types of stress Compression: squeezing (convergent)
Tension: pulling apart in opposite directions (divergent)
Shearing: stress in opposite directions (transform)

7. Isostasy The crust floats on the denser mantle
The gravitational balance of the crust is called isostasy
Isostatic adjustments occur when changes occur in the crust.
When weight is added to the crust it responds by subsiding or sinking
When weight is removed from the crust it responds by rebounding or moving upward

9. 11.2 Folds, Faults, and Mountains
Occur during mountain building
Form due to compression
Most occur in sedimentary rock
Bending of rocks
3 main types: anticlines, synclines, and monoclines

10. Anticlines and synclines are normally associated with each other.
Arching of rock layers
Form ridges
Synclines
Downfolds in rock layers
Sometimes called troughs
Form valleys
Anticlines and synclines are normally associated with each other.

12. Monoclines Very broad folds Large steplike folds
Found in areas that have faults

14. Faults Movement along a fracture
The rock surface that is above the fault is called the hanging wall
The rock surface below the fault is called the footwall.
The area where movement is occurring is called the fault plane
Faults are classified according to the type of movement
There are 4 major types of faults: normal, reverse, thrust, and strike-slip

16. Normal Reverse and thrust Strike slip Occur due to tension
Hanging wall moves down relative to the footwall
Causes extension of the crust
Reverse and thrust
Occur due to compression
Hanging wall moves up relative to the footwall
Causes shortening of the crust
Strike slip
Occur due to shearing
Movement is horizontal

18. Types of Mountains
Folding and faulting produce many of Earth’s mountains
Mountains are classified by the processes that formed them.
Orogenesis: processes involved in mountain building
Groups of mountains
Range: group of similar mountains
System: a group of mountain ranges
Belts: large groups of mountain systems, most are found along the edges of continents

20. Folded Mountains Volcanic Mountains Form by folding due to compression
The Appalachians, Rockies, and Alps are examples
Sedimentary rocks are common
Volcanic Mountains
Form along plate boundaries and at hot spots
Contain igneous rocks
Aleutian Islands, Hawaii, Mid Ocean Ridge, Cascades

22. Fault Block Mountains Form due to movement along normal faults
Formed by tension at a normal fault
The valleys formed are called grabens.
The uplifted areas are called horsts.
Sierra Nevada Mountains

25. Plateaus form when an area of the crust is uplifted vertically
Plateaus form when an area of the crust is uplifted vertically. Commonly contain sedimentary rock.
Domes are caused by bending upward of sedimentary layers. Commonly contain igneous and metamorphic rock.

26. 11.3 Mountains and Plates Convergent Boundary Mountains
Most mountains form at convergent plate boundaries
Colliding plates produce compression
When subduction occurs, volcanic mountains commonly form on the overlying plate

27. Oceanic – Oceanic Convergence
Produce volcanic island arcs
Subduction zones and trenches form at the boundary
The more dense oceanic crust is subducted
Aleutian Islands
Oceanic – Continental Convergence
Produce continental volcanic arcs and folded mountains
Oceanic crust is always subducted
Cascades, Rockies, and Andes

28. Continental – Continental Convergence
Folded mountains form
Both crusts will build up because continental crust is not dense enough to be subducted.
Himalayas and Appalachian

29. Divergent Boundary Mountains
Usually formed on the ocean floor
Forms the mid ocean ridge.
Divergent boundaries form fault block mountains
Volcanoes formed at a divergent boundary are called fissure or rift volcanoes
Non-Boundary Mountains
Hot spot volcanoes that form over a mantle plume
Hawaii

30. Continental Accretion
Accretion: occurs when material is scraped off of a subducted plate and combines with the land.
Enlarges continental land masses
Any crust that has become embedded into a continent is called a terrane.
Terranes have a geology that is different from the continent that it is attached to.