Do Now 2/26/14 What do contour lines on a topographic map indicate? If one line on a topographic map reads 200 km and the next line reads 250 km, what is the index contour? How can metamorphic rocks form?

Weathering of Rocks 2 main types Mechanical weathering requires physical forces to break rocks into smaller pieces. Chemical weathering requires the transformation of rock into one or more new compounds.

Mechanical– Frost Wedging water forces its way into the cracks water freezes which causes the crack to expand more water fills the cracks & freezes rocks split apart

Mechanical Weathering – Unloading & Exfoliating rocks are uplifted and the rock surface is eroded away dome shaped rock outer edges are cracked and break loose – exfoliating.

Mechanical Weathering – Biological Activity plants & animals burrow through the rock humans blast rocks apart looking for minerals & deforestation dead organisms produce acids that dissolves the rock

Chemical Weathering – Water Most important agent of chemical weathering dissolves various gases from the atmosphere and soil causes a reaction with minerals in the rocks Oxygen reacts with the metals in the rocks to produce oxide (rust) to create a yellow to reddish-brown rocks Acids dissolve away the surface of the rocks

Chemical Weathering – Spheroidal Weathering Rocks are eroded by water & become rounded outer straight edges will always erode away first

Rate of Weathering Rock characteristics - granite rocks are more resistant to weathering while marble (calcium carbonate) dissolves easily with acid rain Climate Temperate climates have greater frost wedging & chemical weathering Influences the types of vegetation that grows in the area Dry, arid climates & polar climates have slow weathering of rocks

Differential Weathering Softer minerals will wear away quicker leaving peaks & holes in the rock structures Areas with more cracks will break apart more quickly

Lab – Weathering of Rocks Assignment Lab – Weathering of Rocks

Partner work. You have to draw a diagram of the rock cycle. It must have: Color Be labeled Have descriptions at each step

Exit Ticket 2/26/14 Imagine that you are going on a rock climbing expedition. Take the information you gathered from different texts which involve the rock cycle and decide which of the three types of rocks you would feel the safest climbing and explain why you chose that type of rock. Expand your answer to include why you did not choose the other two types of rocks as well.