Ch 17 (Part II) SHORELINES a)Waves b)Longshore transport c)Erosional shores d)Depositional shores e)Emergent and submergent shor f) Sealevel rise
Dec 21, 2015
Ch 17 (Part II) SHORELINES
a) Wavesb)Longshore transportc) Erosional shoresd)Depositional shorese) Emergent and submergent shoresf) Sealevel rise
= orbital wave (waves of oscillation)
Energy advances
But:
Water does not!Water moves in circular orbits
=
erosion
Ocean WAVES
a) Wavesa) WavesShorelinesShorelines
Waves ‘feel’ bottom when it comes to within half of the wavelength
Wave length decreases, wave height increasesAt critical point the wave becomes too steep and breaksSurf sloshes onshore
Breaking WAVES
Fig. 17.13
a) Wavesa) WavesShorelinesShorelines
Wave refraction strongly influences erosion and sediment transport
Waves travel more slowly in shallow water so they refract towards
the beach.
a) Wavesa) Waves
Waves refract around headlands, increasing
wave impact on headlands, decreasing it
on beaches. Fig. 17.13
Longshore transport • Swash is oblique,
backwash straight, causing beach drift of sediment along the shore
• Oblique waves also cause longshore currents parallel to beach
b) Longshore transportb) Longshore transport
Beaches = Rivers of sand!Beaches = Rivers of sand!
ShorelinesShorelines
Wave refraction along an irregular shoreline
• Wave energy is concentrated at headlands and dispersed in bays
• Causes erosion of headlands and creation of erosional features Figure 10-14b
c) Erosional Shoresc) Erosional ShoresShorelinesShorelines
Fig. Story 17.13
• Headland• Wave-cut cliff• Wave-cut
terrace (bench)
• Sea cave• Sea arch• Sea stack
c) Erosional Shoresc) Erosional ShoresShorelinesShorelines
ShorelinesShorelines
BEACHES
• Source of beach sediments
- rivers- cliff erosion- marine life
• Sand composition
d) Depositional Shoresd) Depositional Shores
Beaches
See Fig. 17.18
ShorelinesShorelines
BEACHES
• Source of beach sediments
- rivers- cliff erosion- marine life
• Sand composition
d) Depositional Shoresd) Depositional Shores
See Fig. 17.18
• Spit
• Bay barrier (baymouth bar)
• Tombolo
• Barrier island
• Delta
d) Depositional Shoresd) Depositional ShoresShorelinesShorelines
Emergent coasts
Develop because of uplift of an area or a drop in sea level
Features of an emergent coast– Wave-cut cliffs
– Wave-cut platforms
e) Emergent and submergent coastse) Emergent and submergent coasts
Uplifted, ancient wave-cut benches exposed in southern California
e) Emergent and submergent coastse) Emergent and submergent coasts
Submergent coast
Caused by subsidence of land adjacent to the sea or a rise in sea level
Features of a submergent coast– Highly irregular shoreline
– Estuaries – drown river mouths
e) Emergent and submergent coastse) Emergent and submergent coasts
Chesapeake Bay is a good example of a submergent coastline
e) Emergent and submergent coastse) Emergent and submergent coasts
f) Sea-level risef) Sea-level rise
Fossil fuel burning has added greenhouse gases to atmosphere
Sea-level rise: thermal expansion of seawater and ice-sheet melting, 4mm/yr, 20-90 cm during this century
Global warming follows(up to 0.6 C in past century)
Chapter 17: Earth beneath the ocean
The area labeled “W” is the __________.A. abyssal plainB. continental riseC. continental shelfD. continental slope
WX
Y
Z
Chapter 17: Earth beneath the ocean
The area labeled “X” is the __________.A. abyssal plainB. continental riseC. continental shelfD. continental slope
WX
Y
Z
Chapter 17: Earth beneath the ocean
The area labeled “Y” is the __________.A. abyssal plainB. continental riseC. continental shelfD. continental slope
WX
Y
Z
Chapter 17: Earth beneath the ocean
Which of the following statements is false?
A. Deep-sea sedimentation leaves a more continuous geologic record than continental sedimentation.B. The oceans lack folded and faulted mountains like those on continents.C. The oldest oceanic crust is much younger than the oldest continental crust.D. Weathering and erosion are more important in the oceans than on continents.
Chapter 17: Earth beneath the ocean
In which of the following locations would you most likely find outcrops of basalt on the ocean floor?
A. on the abyssal plainB. on the continental riseC. on the continental shelfD. on the flank of a rift valley
Chapter 17: Earth beneath the ocean
A traverse from North America across the Atlantic Ocean to continental Europe would reveal that the ocean floor ____________.
A. has high undersea mountains near both continents and is flat in the middleB. has deep trenches near both continentsC. has a number of active volcanoes along most of the width of the traverseD. is approximately symmetric about the Mid-Atlantic Ridge
Chapter 17: Earth beneath the ocean
Graded beds of sand, silt, and mud deposited on submarine fans are called ______.
A. alluvial fansB. dunesC. tillsD. turbidites
Chapter 17: Earth beneath the ocean
Which of the following materials would one expect to find on a continental shelf at a passive margin?
A. basaltB. pelagic sedimentsC. terrigenous sedimentsD. volcanic ash
Chapter 17: Earth beneath the ocean
What are foraminifera shells, the most abundant biochemically precipitated pelagic sediment, made of?
A. calcium carbonateB. silicon dioxideC. sodium chlorideD. iron sulfide
Chapter 17: Earth beneath the ocean
Which of the following forms a barricade between the open ocean and the main shoreline?
A. abyssal hillsB. barrier islandsC. guyotsD. wave-cut terraces