Structure labs/drawing

• Recent labs often “sloppy”• Not taking time to draw contacts properly

– Units must maintain thickness– Contacts should be parallel and “smooth”– Contacts should be in the right place– Angles should be approximately correct (use

a protractor if you cannot draw angles to within 10°) and consistent

Drawing a strike and dip symbol

What is the orientation determined?

115/37 NE

Drawing a strike and dip symbol115/37 NE

What is the strike?

115

What is the dip direction?

NE

What is the dip?

37

Done!Remember that if it is a cleavage measurement, the symbol is like this…

N

Geological maps

Wolfville mapInformation is available on the:

MAP

…on the

LEGEND

…and on the CROSS-SECTIONS

Also some more detailed information

in the

“Descriptive Notes”

Section A

• 11 (relatively straightforward) questions.• Some hints

– Use the legend and cross-sections– “a deep well” means hundreds of metres (scale of the

cross sections)– Contacts are:

• Conformable (bedding)• Cross cutting (faults, intrusions, unconformities)

– For question 10, think of the rule of vees– For question 11, think of your fieldtrip to Black River

At a spreading ridge

Between the ridge segments

Active relative motion on the fault BUT in the opposite sense to the “offset” of the ridge

Away from the ridge segments

Plates are moving BUT in the same direction and thus faults are not tectonically active (a “fracture zone”)

Right lateral fault…

• Fault on which the “other side” appears to have moved to the right.

Symbol for right lateral fault

Left lateral fault…

• Fault on which the “other side” appears to have moved to the left.

Symbol for left lateral fault

Plate tectonic animation

Features on the ocean floor…(6e: 32–34; 5e: pp. 227–234)

• Abyssal plain = flat portion of the deep ocean (away from spreading ridges)

• Continental shelf = portion of the continental crust that is submerged

• Continental slope = the marked change in slope of the ocean floor that indicates the change from continental crust to oceanic crust

• Deep sea fan = a “fan shaped” pile of sediment off shore of major rivers (Amazon, Ganges, etc.)

Features on the ocean floor…(6e: 32–34; 5e: pp. 227–234)

• Mid-ocean ridge = the high range of mountains that runs under the oceans and is the site of “spreading”

• Seamount chain = line of undersea peaks that extends from a “hot spot” in the mantle (only one end of the chain can be volcanically active and there is no associated “trench”)

Features on the ocean floor…(6e: 32–34; 5e: pp. 227–234)

• Transform fault = fault that offsets spreading ridges

• Trench = the over deepened portion of the crust where an oceanic plate is “diving” into the mantle (associated with a volcanic arc)

• Volcanic arc = A (usually arcuate) line of volcanoes (all can be active at any one time) usually associated with a trench