Page 325 - Laboratory Manual in Physical Geology

South to North to
Lake Erie Lake Ontario
Queenston
Shale (Brown)
Escarpment 0 NIAGARA RIVER
Whirlpool NIAGARA
Sandstone Lockport GORGE
Niagara 50 Dolostone
Feet below edge of Niagara Falls 150 dolostone

Mudstone
North 100 Rochester

sandy
Lockport 200 mudstone NIAGARA
Dolostone RIVER
(Green) 250 Sandstone
Whirlpool

mudstone
Niagara Gorge 300

FIGURE 11.10 Cross Section of Niagara Falls. Niagara Falls
exists because the named rock units beneath the falls vary in their
hardness (resistance to erosion). As the hard dolostone caprock is
undercut by erosion of the softer mudstone beneath it, pieces of
0 1 2 km the caprock break off and the falls moves upstream.

Goat Is.
Niagara
Falls
ACTIVITY
Niagara River
11.6 Flood Hazard Mapping,
FIGURE 11.9 Geology of the Niagara Gorge Region. The Assessment, and Risk
Niagara River flows from Lake Erie north to Lake Ontario and forms
the border between the United States and Canada. Niagara Falls is THINK |
located on the Niagara River at the head of Niagara Gorge, about How do geologists determine the risk of
About It flooding along rivers and streams?
half way between the two lakes.
OBJECTIVE Construct a fl ood magnitude/frequency

graph, map floods, and flood hazard zones, and assess

Mass Wastage at Niagara Falls flood hazards along the Flint River, Georgia.

Mass wastage is the downslope movement of Earth
PROCEDURES
materials such as soil, rock, and other debris. It is
1. Before you begin , read Flood Hazard Mapping,
common along steep slopes, such as those created where
Assessment, and Risks below. Also, this is what
rivers cut into the land. Some mass wastage occurs along
you will need :
the steep slopes of the river valleys. However, mass
wastage can also occur in the bed of the river itself, as it ___ calculator
does at Niagara Falls. ___ Activity 11.6 Worksheets (pp. 307–310 ) and
The Niagara River flows from Lake Erie to Lake pencil with eraser

Ontario ( FIGURE 11.9 ). The gorge of the Niagara presents 2. Then follow your instructor’s directions for

good evidence of the erosion of a caprock falls, Niagara completing the worksheet.
Falls ( FIGURE 11.10 ).

Stream Processes, Landscapes, Mass Wastage, and Flood Hazards ■ 295