Unit 1: Land & Water Forms World Geography 3200/3202

Intro In this lesson you will: Explain how compressional forces create fold mountains. (k) Differentiate between the terms anticline and syncline. (k) The basis for today’s lesson will be page 13 in your text. The main ideas in this presentation will be taken from material outlined there. First a review from Friday……

Mountain Building Q. Generally, most mountain ranges are on the margins of the continents. Why?? A. Continental plates lie alongside oceanic plates & are compressed against them (rock layers are squeezed upward as a result, producing a mountain) Geologists study three main methods used to create mountains from the Earth’s rocky crust

1. Folded Mountains Most major mountain ranges were formed by folding: a process in which the Earth's plates are pushed together in a roller coaster like series of high points & low points With folding, the continental plates collide causing the thin crust (lithosphere) to bend. The Appalachian Mountains and the Atlas Mountains were formed by folding when North America & Africa collided 400 million years ago.

Folded Mountains All rock that is put under extreme pressure for long periods of time (thousands or millions of years) will fold like clay. Folding bends many layers of rocks without breaking them. The peaks are known as anticlines while the valleys are known as synclines.

Folded Mountains The Rocky Mountains are a prime examples of Folded Mountains How Stuff Works Video Assigned reading p. 13.

Folded Mountains Review Q. What type of tectonic force is required to create folded mountains? A. Compressional Q. What name is given to the peaks created in folded mountains? A. Anticline Q. What term is given to the valleys created in folded mountains? A.Syncline

Folded Mountains Review Q. Are many of the worlds mountains formed by folding? A. MOST Q. How long does it take for folded mountains to form? A. 1000s of years Q. At which type of tectonic zone would you find folded mountains? (ridge, transform or subduction) A. SUBDUCTION

Unit 1: Land & Water Forms World Geography 3200/3202

In this lesson you will: Explain how tensional forces create a normal fault. (k) Explain how compressional forces create reverse and overthrust faults. (k) This lesson corresponds to the information contained in the "Mountains Formed by Faulting" section found on page 14 of your text.

Fault Lines Fault lines are basically great cracks in the earth’s crust created when plates are compressed against each other. The break or crack may be slight or may run deep into the Earth’s crust The length of the fault may be short or may extend hundreds of kms.

Faulting Faulting is instrumental in mountain building Geologists have analyzed the precise ways in which plates are changed by faulting & have developed four main types of mountains

1. Normal Fault Mountains Caused by: tensional forces. Occurs when: A plate on one side of the fault drops down lower than the plate on the other side

Fault Block Mountains Sometimes two normal faults occur parallel to each other In some cases the broken plate between the faults drops as the broken plates move away from each other forming a rift valley In case when many layers of the Earth's crust are moved vertically upward between two parallel fault lines, Fault Block Mountains result. The vertical force is caused by the Earth's internal pressure.

Reverse Fault Mountains If simple rock layers around a fault push against each other instead of pulling away, one block can be pushed up over the other This results in the creation of a Reverse Fault Mountain caused by compressional forces where plates move together at the fault.

Overthrust Faults If the plate that suffers the fault has already undergone folding, & its folded layers are then push up & thrust over layers on the fault’s other side, an Overthrust Fault occurs.

Faulting: A Review Q. What name is given to large cracks in the earth's crust? A. FAULT LINES Q. What name is given to faults formed by tensional forces? A.NORMAL FAULTS Q. What name is given to faults formed by compressional forces? A. REVERSE FAULTS Q. How do overthrust faults differ from regular reverse faults? A. THEY WERE FOLDED BEFORE FAULTING