What is this geomorphological form located at Vitrolles, France?
And how is it formed? It is like a 'raised flat land', or a base of a hill where the top 80% is cut, leaving only the wide, flat base.
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There are a couple of possibilities, depending on what you're paying the most attention to. This falls in an overlap area of terms that vary from region to region and even from person to person.
The key thing to notice in your photo is the whitish band running along the top of the escarpment that borders your landform. This shows that it's held up by a resistant, mostly horizontal, layer of sedimentary rock.
(generalized cuesta image from Wikipedia)
"Plateau" is also plausible, but this is not very specific. The landform in your picture doesn't have quite the extent of the Colorado Plateau.
Tableland or table is probably the most generic name for the entire regional structure under the rock layer.
(Wikipedia image of a mesa in Monument Valley)
There is a similar and bigger chalk plateau at "plateau d'urle" in France.
That one looks like a "chalk plateau of continental shelf origin with straight channels eroded into the underlying clays", by it's flatness and proximity to the sea. The geologists write that the chalk is a freshwater lake chalk deposit due to it's fossils.
The sediments are layed down by different processes with different chemistries... Very tough pure chalk, softer chalk and silt deposits vary in bands, corresponding to underwater currents and rivers that vary over time.
The top layers erode away leaving a very tough protective chalk. The water flow at Vitrolles has stayed shallow, so that it has not tunneled deep under the chalk cap, it has burrowed straight channels just under and through it.
top layer (freshwater lake chalk) 60 million years... red stripes: Calcaires de Vitrolles (Montien-Tertiaire)
lower layer (clay and sandstone) 65-70 million years ... beige no stripes: Argiles et grès à lentilles calcaires (Rognacien-Secondaire)
If the flat land formed as a river terrace, we could call it a raised terrace.
If the flat land is a resistant layer of rock, then we could call it a low plateau. (the thin layer of white rock immediately below the land surface might suggest this is the correct interpretation.)
If it formed by erosion in the past, it could be a peneplain.
The correct word depends on the origin of the feature.
I couldn't find any paper describing the geomorphology of the zone, but this is refered as Plateau de Vitrolles; there is an archaeological deposit close to the point you marcked (source).
You can find a french geologic definition of plateu at this site. I guess the term is equivalent to plateau on US reference bibliography, but there migth be some little differences.
To shortly answer your question about how was it formed, the Ruisseau du Bondon excavated the plateau, forming the slopes and the valley.
To deeply answer a reference to a local geomorphologic study would be needed. There should be some study on geomorphology journals, as the zone looks interesting. If you are at University you could make a research for "Plateau de Vitrolles" and you migth find a complet explanation from local geologists.
Your marker seems to indicate an escarpment, which is a long ridge where a cliff or a steep slope separates low ground from higher ground. These slopes or cliffs can have a number of different causes, but as I have never visited the one in your photo I wouldn't like to hazard a guess as to what caused this particular one.