Sand dunes at Karioitahi Beach
At this site, you will see petrified sand dunes that has been impacted by erosion.
Karioitahi Beach and Kaiotahi Cliffs are fossilized sand dunes that show clear signs of erosion in many places.
What is Erosion?
Erosion is the geological process in which earthen materials are worn away and transported by natural forces such as wind or water.
In other words: erosion is a transformation in soil and rocks, or rather, the process of erosion, transport and sedimentation of soil and rocks. It occurs naturally but can be intensified and even provoked by human action.
The classification of erosions is conditioned by factors such as the type of erosive agent (water, winds and living beings), the relief, the geological structure of the eroded terrain and the previous processes to which it was subjected.
Here are some of the main types of erosion:
• Rain erosion
It is the type of erosion caused by rainwater. In fact, precipitation water is the major responsible for 7 processes. Rain causes the natural erosion of the rocks and aggravates the process of erosion of soil degraded by human action. The proportion of erosion, therefore, depends not only on the intensity and volume of rainwater, but especially on the type of treatment given to the terrain.
• River erosion
It is caused by the water action of the rivers and streams and deepens the valleys in relation to the surrounding lands. River erosion is aggravated when the riparian forest is removed, because the banks are worn by the force of the waters, which intensifies the silting processes of the rivers.
• Marine erosion
Caused by the action of the waters of the seas and oceans, marine erosion causes the erosion of coastal rocks and soils, contributing to the formation of beaches and coastal landscapes, such as the cliffs.
• Wind erosion
It is caused by the action of the winds, which, little by little, are displacing particles from rocks and soil and acting in the transport of sediments. This type of erosion is much slower than that caused by water and is more noticeable in places where the climate has low averages of precipitation and humidity.
• Glacial erosion
In regions where there are negative temperatures, there is freezing of the water contained in the surface and in the underground. When the water freezes, its volume increases - it expands -, and this expansion generates the movement in blocks, which causes the material to move. In addition, the water particles contained in the soils when frozen also move, contributing to the erosive processes in these places.
• Gravitational erosion
As its name suggests, this type of erosion occurs on terrain with high slopes, such as in mountain ranges. Materials from the upper areas, by virtue of gravity, "fall" into the lower areas. Depending on the protection of soil or rock and the type of material, this process can be gradual or move large blocks of rock.
Coastal dunes protect the coastline
Dunes are nature's coastal defence.
Most beaches are backed by vegetated sand ridges called dunes, built up by dry beach sand blown inland and trapped by plants and other obstructions. As sand accumulates, the dunes become higher and wider.
Plants play a vital role in this process, acting as a windbreak and trapping the deposited sand particles. A characteristic of these plants is their ability to grow up through the sand and continually produce new stems and roots as more sand is trapped and the dune grows.
In our haste to get to the water we often over look the amazing vegetation that assists in the forming and shaping of the dunes .
The dune vegetation captures and traps wind blown sand. Holding sand'bank'for future erosion events.
Their masses of intertwining roots stabilize the sand and most importantly assist in beach recovery after an erosion event .
Without these plants much of the sand would be blown away .
Coastal dunes
Stable sand dunes play an important part in protecting the coastline. They act as a buffer against wave damage during storms, protecting the land behind from salt water intrusion. This sand barrier allows the development of more complex plant communities in areas protected from salt water inundation, sea spray and strong winds.
The dunes also act as a reservoir of sand to replenish and maintain the beach at times of erosion.
The sensitive side of the beach
Frontal sand dunes are vulnerable. The vegetation can be destroyed by natural causes such as storms, cyclones, droughts or fire, or by human interference such as clearing, grazing, vehicles or excessive foot traffic. If the vegetation cover is damaged strong winds may cause 'blowouts' or gaps in the dune ridge. Unless repaired, these increase in size; the whole dune system sometimes migrates inland covering everything in its path. Meanwhile, with a diminished reservoir of sand, erosion of the beach may lead to coastal recession.
To avoid this, protecting the vegetation is vital.
For this reason damaged and sensitive dunes might need to be fenced and access tracks for vehicles and people provided. For the sake of our coast we must care for our dunes.
To log this EarthCache, please follow these instructions:
You can park your car at the parking coordinates. Don't walk into the dunes. You can see all answers from the footpath.
Answer the following questions by sending a message through the Geocaching message center or email, with answers (in english or german please) to my profile within 14 days (or the log may be deleted). I’ll respond if something is not clear. Have fun
You can log your find immediately and you must also add a picture of yourself or your GPS at the location (compulsory).
QUESTIONS:
1 - What type (s) of erosion could occur along the coast here? Describe it with your own words
2 – Watch the shore line and describe what influence the erosion has on Karioitahi Beach and Kaiotahi Cliffs (do you watch increasing or decreasing of sand arround the limestone)
3 - Erosion often shows marked lines in the rock. Are these lines horizontal, vertical or diagonal?
4 -Why are stable sand dunes important? Explain your opinion in own words.
Enjoy your stay and have fun.