Rocky Coast_ Tectonics

Narrow contiental shelf give you what?

High Wave energy

Volcanic Islands

Limited sediment and steep topography

Sea Arch

An opening cut through a headland by dissolution and wave erosion

Talus

Can protect the baseline of the cliff

Concordant

conformable, when referring to plutonic bodies, indicates that the intruding magma of sills and laccoliths lies parallel to rather than cutting across country strata, as do discordant structures such as veins, dikes, bysmoliths, and batholiths.

Non-lithology

not as steep

Spectacular Mophology

A arch or stack in a rock PPT 4 Slide 3

Wave cut platform

A gently sloping surface exposed at low tide, created by the erosional retreat of a coastal cliff.

Tectonically Inactive Margins

Along wide and flat continental shelves (e.g. Australia's southern and eastern coast) Inactive cliffs that were formerly active during sea level highstands and now fronted by other coastal deposits (e.g. beach)

Shore Platforms

Type A: Sloping shore platform (1-5 degrees), macrotidal environments, low slope erosional surface extending from base of cliff seaward 1.) Microtidal coast 2) Mostly <0.5 calm weather seas 3) Intermittent high energy events >1.5 m 4) Average lowering of 1.4 mm/yr using micro erosion meter (MEM) but subaerial weathering highest contributor, waves less important (are attenuated farther offshore due to bathymetry) 5) Dominant process subaerial weathering, waves attenuated too far offshore by bathymetry to to explain the platform lowering Type B: Sub-horizontal platform, micro and mesotidal environments, erosional surface terminates seaward with a marked scarp

What are the 8 Physical Processes

Wave impact: wave directly impacts a cliff or sloping exposure (dynamic pressures) Hydrostatic pressures: mass of water (may alternate with rising and falling water levels) Air compression: air is trapped between rock surface or in fractures against the wave water (pneumatic stresses) Wave quarrying: removal/plucking of fragments by waves (small or large)abrasions, and Wave-Cut Notche Abrasion (corrasion): fragments (small and large) crashing against an exposure Attrition: breakdown associated with impact stresses from particles carried by waves Freeze and Thaw: 9% expansion of ice Crystal growth: from salt water

Wave- Cut Notch

Wave-cut notches in mudstone and limestone bluffs, Tierrabomba Island, west side of Cartagena Bay, Colombia. Notches and the longer term evolution of coastal profiles Waves attack the base of a cliff through the processes of abrasion, corrosion, hydraulic action The cliff becomes undercut and wave cut notch is formed Eventually the cliff becomes unstable and collapses, Further cliff retreat will form a wave cut platform PPT 4 Slide 26

Why in the past was Rocky Coast just observational?

We did not have the technology to obtain accertate readings of the small changes happening along those coast lines. These structures have been changes very little over the last 10million years.

Tidal Range

Where does the wave energy become focused? Would diurnal or semi diurnal tides affect how the energy is expended

Rocky Coast

bedrock cliffs rise from water's edge. They create at lot of morphologies and lithologies. They are very active along tectonic margines 60-80% of the worlds coast is dominated by RC. High energy waves Cliff Hight Erosional environments, may locally have pocket beaches or deposition environments but mostly erosional. Dominated by land ward retreat with vertical faces plunging into deep water. Steeply sloping shoreline with no real clear definition separating a slope from a cliff. Retreats to rock ledge or shore platform at or close to sea level. May be subhorizonatal or slope gently seaward . Characteristically: erosion exceeds clastic sedimentation or low sediment supply or sediment loss

How do we explain mulitiple Terraces?

form when stream downcuts through previously deposited alluvium - downcutting stream carves new, lower floodplain, leaving behind older floodplain and terrace - with significant downcutting, multiple terraces can result

Plugging Cliff line

that just drops into water with no real start or platform

Why are Rocky Coast more active along active margins such as California?

An active coastline has a subduction zone that creates a narrow shelf. That shelf creates high wave energy. The wave energy along with the uplift creates things like cliff lines and different strong lithoglies.

Sea Stack

An island of rock eroded from a headland.

RC: secondary depositional effects

Coast has been smoothed by strand plains formed between bedrock headlands

Glaciated Coasts

Deeply scoured, with little sediment left behind

How can you create subaerial processes?

Depending on how the tide or system effects the marine process it can lead to subaerial processes such as mast wasting.

Lithology of Rocky Coast

Interbedded Ordovician phyllite and quartzite lithology at the Ovens, NS Cambrian and Ordovician rocks of the Meguma Lithostratigraphic Terrane Abrasion of vertically tilted sedimentary rocks, interbedded rocks of different lithology, Notice the strike and vertical dip of the rocks, does this geometry and variability in lithology explain aspects of the coast? Lithostratigraphic variability and structural trend variability

Techonic Margins/Rocky Coast

Limited sediument imput becasue it is new coast line so the drainage basin is new. You also get uplift so you get high preservation material Uplift Volcance island

What drive the coastal morphology?

Lithology and Lithologic Variability: eg. differential erosion Structural Trends: faults, folds, fractures Waves: energy and dominant approach Tidal Range: duration of time that waves impact a given elevation Mass Movements: overall stability of the cliffs, rockfalls and slides Biota: boring organisms? Chemical Processes: interaction with seawater Climate: weathering rates RSL: up, down, stable?

How does boundary conditions affected evolution?

Sea level: not static during millennial timescales of rocky coast evolution 2. Geology: resisting force vs. assailing forces 3. Groundwater flow: may affect erosional resistance or promote mass movements 4. Climate: temperature and humidity affect physical, biological, and chemical weathering 5. Tides and Waves: significant annual wave height, storm waves, tidal range (microtidal vs. macrotidal)

Bioerosion

Occupation of the Intertidal Zone along the Oregon Coast Seaweed/Algae holdfasts penetrate between grains and Into mineral cleavage planes: geophycology (seaweed-bedrock interactions including resultant weathering); swaying seaweed in the waves may also accentuate physical weathering

Structural Control

PPT 4 Slide 39

Marine Terrace Model formation

PPT 4 Slide 46

Low Latitude, uplifted reef coasts

Paleo reefs that are now subaerial

Sub-marine Processing

Processes happen at or above the water line

Marine Processing

Processes happening under the waterline

Lithology

Steep Dominated by erosion not so much by deposition It has sed. loss or none

Barrie Island

Steep Slopes regardless of lithogy.

The two main type of Processing for Rocky Coast

Sub-marine Marine

How did the 12 Apostles of the SW Australian Coast devop?

These are sea stacks now. They formed by the breakdown of a rock arch. That arch can delvope by fracture points, waves,and possiably refraction points within wave energy

Promontory

Thy controle they wave momentum you get by refraction within the embayment. *Picture in Notes

What are the 2 ways Rocky Coast can be broken down?

" Hardrock Coast" Part of rocky coast that have really resistant lithology. It is very lithified and cohesive. " Softrock Coast" - Less resistant lithology and is less lithified and cohesive Not a lot of sediment so beaches are unlikely to happen

Active Margins

-Coasts are located between mountain belts and deep sea trench: small drainages (less sediment) -Narrow continental margins with submarine canyons through which sediment can be lost -Wave energy not effectively dissipated prior to reaching the coast -Tectonic activity: rapid uplift or subsidence, typically uplift

What are the steps to ersion

1. Erosion preference along base and vertical fractures 2. Caves happen with erosional processes produces caves within the headland 3. Caves connect and a series of hold form as a consequence of terrain over the caves collapsing 4. Due to instability the collapse leaving . behind a sea arch. over time the arch can lead to a sea stack

What affects Rocky Coast Evolution?

1. Lithology 2. Structural- Faults, fractures 3. Wave- energy, direction of approach a. Tidal energy and type b. mass movement c. mass movenment d. biota- bioerosion e. chemical processes f. chemistry of seawater vs. bedrock g. climate- control on the organisms( in warm weather this creates chemical weathering and cold it is physical weathering)

The 2 main Classe or Rock Coastline/ Shore Platforms

1. Shore Plateforms Type A: (Slopping Shore) - 2-5 degree slopping Type B: (Sub-horizontal) type environment where the erosion surface termatiates seaward. Where land starts at the base and then just drops in deep water. 2. Plunging Cliff

What places can Rocky Coast exist?

1. Volcanic Islands 2. Glaciated Coast- It has been stripped off 3. Low Latitudes- like acient reefs that have been uplifted 4. Active Margins 5. Tectonically Inactive Margins

What are the Physical and chemica lProcesses

1. salt weathering Most effective in what types of climate? 2) oxidation of minerals (become less resistant to weathering)

What are the 3 morphology for rocky coast?

1.Shore Platforms 2. Plunging Chiff 3. Sub-horizontal platform ( which is apart of shore plaforms.

Types of down slope Movement

Falls: free falling blocks Topples: little free fall, rotation of block around a hinge line Slides: here shown as rotational slumping but can also be a planar slide Mudslide: otherwise known as flows, no block movement due to shearing within the body

Physical Processes:

Freeze and thaw contributing toward downslope transfer of material (mass wasting)?

Subaerial

mainly used in geology to describe events or features that are formed, located or taking place on the Earth's land surface and exposed to Earth's atmosphere.

Glacial Tills

non- cohesive but still creates a structure

Non-cohehsive

not fully lithified like glacial tills