"The Downs were formed under periglacial (around a glacier/ice sheet) conditions when the ground was frozen for much or all of the year. In summer, thawing of snow on the surface produced streams which were unable to soak down through the joints and pores of chalk as they do now, because these spaces were filled by ice; so they flowed across the surface, and eroded the thin layer which had thawed. Over thousands of years (and there were several glaciations, each producing periglacial conditions further south, each probably lasting thousands of years) of eroding a few inches a year, this eroded the existing valleys. This was aided by freeze-thaw cycles breaking up the surface rock of the valley sides and floor, making it easier for the streams to erode - the freeze-thaw breaks up the chalk, the stream removes the debris exposing more chalk to the next freeze - thaw cycles and so on. Only when the climate warmed up at the end of each glaciation did the chalk unfreeze at depth, so the water sank into it instead of flowing over the surface, did the valleys become dry."
SOME MISCELLANEOUS NOTES
Peri = ?
perigee | perdi | n. Formerly also in L & Gk forms. L16. [Fr. perigee f. mod.L perig(a)eum f. late Gk perigeion use as n. (sc. diastema distance) of neut. of perigeios close round the earth, f. as PERI- + gaia, ge earth.] (Opp. APOGEE.) 1 Astron. The point nearest to the earth in the path of a body orbiting the earth. (Orig. also used w. ref. to the sun and planets, viewed geocentrically). L16. 2 The point in the sky at which the sun has the lowest altitude at noon (i.e. at the winter solstice). Only in M17. 3 fig. A lowest point, a nadir. rare. M17.perigean a. of or pertaining to perigee E19.
glacial | le()l, -sl | a. & n. M17. [Fr., or L glacialis icy, f. glacies ice: see -AL1.] A adj. 1 Of the nature of ice; (partly) consisting of ice; cold, icy, freezing (lit. & fig.). M17. 2 Chem. Crystalline (arch.); (esp. of pure acids) tending to form crystals resembling ice. Now chiefly in glacial acetic acid. M17. 3 Geol. Characterized or produced by the presence or agency of ice in the form of glaciers; pertaining to glaciers. M19. 4 Of movement, progress: resembling that of a glacier, very slow. E20.
glacier | las, les- | n. M18. [Fr. (earlier glaciere), f.
glace ice, f. Proto-Romance alt. of L glacies ice: see -IER.] A slowly
moving mass or river of ice formed by accumulation and compaction of snow
on higher ground.
hanging glacier: see HANGING a.
Comb.: glacier burst the sudden release of water impounded by a glacier; glacier mill = MOULIN; glacier snow: at the upper end of a glacier, not yet compacted into ice.
glaciered a. covered with glaciers E19. glacieret n. a small alpine glacier L19. glacierization n. (a)rare conversion into a glacier; (b)the covering of land by an ice sheet; the state of being so covered: M19
Source: Oxford Dictionary & Encylopaedia (temporary inclusion until the final draft is completed).
In the cold, or periglacial, areas adjacent to and beyond the limit of glaciers, a zone of intense freeze-thaw activity produces periglacial features and landforms. This happens because of the unique behaviour of water as it changes from the liquid to the solid state. As water freezes, its volume increases about 9 percent and can, if confined in a crack or pore space, exert pressures of about 200,000 kilopascals (29,000 pounds per square inch). This is enough to break the enclosing rock. Thus freezing water can be a powerful agent of physical weathering. If multiple freeze-and-thaw cycles occur, the growth of ice crystals fractures and moves material by means of frost shattering and frost heaving, respectively. In addition, in permafrost regions (see below) where the ground remains frozen all year, characteristic landforms are formed by perennial ice.
Felsenmeers, talus, and rock glaciers.
In nature, the tensional strength of most rocks is exceeded by the pressure of water crystallizing in cracks. Thus, repeated freezing and thawing not only forms potholes in poorly constructed roads but also is capable of reducing exposed bedrock outcrops to rubble. Many high peaks are covered with frost-shattered angular rock fragments. A larger area blanketed with such debris is called a felsenmeer, from the German for "sea of rocks." The rock fragments can be transported downslope by flowing water or fall off the cliff from which they were wedged by the ice. Accumulations of this angular debris at the base ofsteep slopes are known as talus. Owing to the steepness of the valley sides of many glacial troughs, talus is commonly found in formerly glaciated mountain regions. Talus cones are formed when the debris coming from above is channelized on its way to the base of the cliff in rock chutes. As the talus cones of neighbouring chutes grow over time, they may coalesce to form a composite talus apron.
In higher mountain regions, the interior of thick accumulations of talus may remain at temperatures below freezing all year. Rain or meltwater percolating into the interstices between the rocks freezes over time, filling the entire pore space. In some cases, enough ice forms to enable the entire mass of rock and ice to move downhill like a glacier. The resulting massive, lobate, mobile feature is called a rock glacier. Some rock glaciers have been shown to contain pure ice under a thick layer of talus with some interstitial ice. These features may be the final retreat stages of valley glaciers buried under talus.
Source: Encyclopaedia Britannica (temporary inclusion until the
final draft is completed).
Fossil Sea Urchin Echinocorys scutatus
Flint on Shoreham Beach
With the longshore drift and
changing coastline, I suspect it came from somewhere else. Shingle
banks have enabled surveyors to find out where the coast used to be to
a certain extent.
Aequipecten aspera (pic) like a scallop impression
Ammonite Scvloenbachia varians (pic.): particular level of chalk
Large ammonite Acanthoceras rhotomagense 8 ft deep