17: Shorelines (Exercises)

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Q17.1 Wave Height versus Length

This table shows the typical amplitudes and wavelengths of waves generated under different wind conditions. The steepness of a wave can be determined from these numbers and is related to the ratio: amplitude/wavelength.

1. Calculate these ratios for the waves shown. The first one is done for you.

2. How would these ratios change with increasing distance from the wind that produced the waves?

Amplitude	Wavelength	Ratio
m	m	ampl./length
0.27	8.5	0.03
1.5	33.8	0.04
4.1	76.5	0.05
8.5	136	0.06
14.8	212	0.07

Within increasing distance from the source the wave heights would gradually decrease and so the ratios would decrease.

Q17.2 Wave Refraction

[SE]

Q17.3 Beach Forms

Barrier islands could from if this was a low-relief coast with an abundant supply of sediment from large rivers.

Possible locations of coastal deposits [SE]

Q17.4 A Holocene Uplifted Shore

The melting of glacial ice around the world at the end of the last glaciation (between 14 and 8 ka – see Figure 17.25) led to relatively rapid sea-level rise (by a total of approximately 125 m) which resulted in this area being submerged. That was a eustatic process. In response to the loss of ice in this region of coastal British Columbia there was a slower isostatic rebound of the crust, which is why this area is now back up above sea level.

Q17.5 Crescent Beach Groynes

[SE]