EN
⚠️ Warning:The slopes are unstable and dangerous. Please stay on the marked paths at all times. The terrain can be slippery, especially after rain.
Log conditions and complete the task on site.
Observe the slope from the listing coordinates and answer the following questions.
Question 1:
Which signs of active or past mass movement can you observe on the slope?
Describe at least two observations.
Question 2:
Assign the three visible rock layers to the order “top - middle - bottom” and describe two visible property for each layer that you can observe on site.
Examples: colour, texture, surface appearance, weathering features.
Question 3:
How does water (rainfall and seawater) affect the three rock layers at this location?
Base your answer on what you observe on site and on the visible properties of the rock types.
Question 4:
Why do slope movements occur here, while other coastal sections of Malta remain stable?
Base your answer on the rock types present at this location and the way they interact with water and gravity.
📸 Take a photo of yourself at the location and add it to your log.
Before logging send your your answers by mail or messagecenter. Have fun!
Introduction
The coastline around Qarraba Bay is one of Malta’s most striking geological features. Several rock layers, ranging in age from the Upper Cretaceous to the Oligocene, are exposed here. Together, these layers clearly demonstrate the effects of water, gravity and mass movement on different rock types, rather than the effects of classic coastal erosion alone.
Why are the slopes of Qarraba Bay moving?
The slopes at Qarraba Bay are a prime example of clay-controlled mass movement in a coastal environment. Unlike many other seemingly stable cliff sections in Malta, this location exhibits active and fossilised evidence of slope deformation, resulting from the interaction of three distinct rock layers. A hard limestone plateau sits on top of a soft, impermeable clay layer. When water enters this clay, it loses strength and begins to deform plastically under the weight of the overlying rocks.
This EarthCache shows that slope instability is often caused by internal geological processes such as saturation, gravity, and contrasting rock properties, rather than by erosion alone. The movement here is slow but continuous, reshaping the landscape over time. By observing the slope from a safe distance, visitors can learn to recognise signs of past and active mass movement. Signs of past and active mass movement; understand how different rock types react to water, and explain why this part of the Maltese coastline behaves differently to the more stable limestone cliffs nearby. The logging tasks will guide you step by step through these observations, helping you to connect what you see on site with the geological processes responsible for this constantly changing slope.
Geological background
There are three clearly recognisable layers on site:
Upper Coralline Limestone Colour: light beige to whitish Properties: very hard, compact limestone. Significance: forms the stable plateau above the bay. When the underlying clay layer gives way, the limestone blocks break off and slide downwards.
Blue Clay Formation Colour: grey to blue-grey, darker when wet. Properties: impermeable, plastic and highly malleable. Significance: crucial for the landscape. When the clay becomes saturated with water, it loses its stability, leading to slow landslides and plastic deformation.
Globigerina Limestone Colour: light yellow to ochre Properties: soft, fine-grained limestone containing fossils. Significance: forms the base of the cliffs and is partially exposed at beach level.
Geological Processes at Work
This site is primarily shaped by mass movement rather than classic coastal erosion caused by wind or waves.
Hard limestone layers overlie a soft clay layer. When the clay becomes saturated, it slowly flows downhill under the weight of the rocks above it. This process produces: undulating, flowing slopes, stress cracks, and small stepsmoist zones where water seeps out.
These processes are ongoing, making the slope a dynamic, constantly evolving geological feature.
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The role of water
Rainwater
Rainwater infiltrates the upper limestone layers, reaching the dense blue clay below. This causes the clay to absorb water, become heavier and lose strength, allowing it to deform and move downslope.
Seawater
Salt spray and seawater moisture penetrate the surface through capillary action, keeping parts of the clay permanently damp. Along the coast, the combined effects of rainfall and seawater create persistent moist zones that further reduce slope stability.
SOURCES
https://continentalshelf.gov.mt/geological-survey/geological-map/?utm_source=chatgpt.com, https://era.org.mt/topic/maltese-landscapes-geomorphology/?utm_source=chatgpt.com, https://era.org.mt/wp-content/uploads/2019/05/Rdumijiet_GhajnTuffieha_ManagementPlan.pdf?utm_source=chatgpt.com
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Text editing and translation with the help of ChatGPT (review by Sawi52)
MA
⚠️ Twissija: Il-għoljiet mhumiex stabbli u perikolużi. Jekk jogħġbok ibqa’ fit-triqat immarkati fi kwalunkwe ħin. It-terren jista’ jkun skivli, speċjalment wara xita.
Irrakorda l-kundizzjonijiet u komplimenta t-tasks fuq il-post.
Iċċekkja b’attenzjoni fuq il-post u għodd il-mistoqsijiet li ġejjin. Osserva l-għolja mill-koordinati tal-listing.
Mistoqsija 1
X’indikaturi ta’ moviment massiv attiv jew tal-passat tista’ tħares fuq l-għolja?
Iddefinixxi mill-inqas żewġ osservazzjonijiet.
Mistoqsija 2
Agħti lis-saffijiet tal-ġebla viżibbli t-tliet livelli “fuq - bejn - t’isfel” u iddeskrivi żewġ proprjetajiet viżibbli għal kull saff li tista’ tara fuq il-post.
Eżempji: kulur, tessut, dehra tal-wiċċ, karatteristiċi ta’ weathering.
Mistoqsija 3
Kif jaffettwa l-ilma (xita u ilma tal-baħar) lis-saffijiet tal-ġebla t-tlieta f’din il-lokalità?
Ibbaża l-għażla tiegħek fuq dak li tara fuq il-post u fuq il-proprjetajiet viżibbli tat-tipi ta’ ġebel.
Mistoqsija 4
Għaliex iseħħu movimenti tal-għolja hawnhekk, filwaqt li sezzjonijiet oħra tal-kosta ta’ Malta jibqgħu stabbli?
Ibbaża l-għażla tiegħek fuq it-tipi ta’ ġebel preżenti f’din il-lokalità u kif jirrelataw mal-ilma u l-gravità.
📸 Ħu ritratt tiegħek f’din il-lokalità u żidha mal-logbook tiegħek.
An er loggien scal þú thíne andwurdon mid brêve edder Messagecenter sendan. Igawdu!
Introduzzjoni
Il-kosta madwar Qarraba Bay hija waħda mill-aktar karatteristiċi ġeoloġiċi impressjonanti ta’ Malta. Hawnhekk huma esposti diversi saffi ta’ blat, li jvarjaw fl-età mill-Kretaċju ta’ Fuq sal-Oliġoċen. Flimkien, dawn is-saffi juru b’mod ċar l-effetti tal-ilma, il-gravità u l-moviment tal-massa fuq tipi differenti ta’ blat, aktar milli l-effetti tal-erożjoni klassika tal-kosta biss.
Għaliex l-għoljiet ta’ Qarraba Bay qed jiċċaqalqu?
L-għoljiet f’Qarraba Bay huma eżempju ċar ta’ moviment tal-massa kkontrollat mit-tafal f’ambjent kostali. B’differenza minn ħafna sezzjonijiet oħra ta’ rdumijiet li jidhru stabbli f’Malta, dan is-sit juri evidenza attiva u fossili ta’ deformazzjoni tal-għoljiet, li tirriżulta mill-interazzjoni ta’ tliet saffi distinti ta’ blat. Plateau ta’ ġebla tal-franka iebsa jinsab fuq saff ta’ tafal artab u impermeabbli. Meta l-ilma jidħol f’dan it-tafal, dan jitlef is-saħħa tiegħu u jibda jiddeforma b’mod plastiku taħt il-piż tal-blat ta’ fuq.
Dan l-EarthCache juri li l-instabbiltà tal-għoljiet ħafna drabi tkun ikkawżata minn proċessi ġeoloġiċi interni bħas-saturazzjoni, il-gravità u l-kuntrast fil-proprjetajiet tal-blat, aktar milli mill-erożjoni biss. Il-moviment hawnhekk huwa bil-mod iżda kontinwu, u maż-żmien jibdel il-pajsaġġ. Billi josservaw l-għolja minn distanza sigura, il-viżitaturi jistgħu jitgħallmu jagħrfu sinjali ta’ moviment tal-massa fil-passat u fil-preżent; jifhmu kif tipi differenti ta’ blat jirreaġixxu għall-ilma; u jispjegaw għaliex din il-parti tal-kosta Maltija taġixxi b’mod differenti mir-rdumijiet tal-ġebla tal-franka aktar stabbli li jinsabu fil-qrib. Il-kompiti tal-loggjar jiggwidawk pass pass f’dawn l-osservazzjonijiet, u jgħinuk torbot dak li tara fuq il-post mal-proċessi ġeoloġiċi li huma responsabbli għal din l-għolja li qiegħda tinbidel kontinwament.
Sfond Ġeoloġiku
Fuq is-sit jistgħu jiġu rikonoxxuti b’mod ċar tliet saffi ta’ blat:
Upper Coralline Limestone (Ġebla tal-Franka Korrallina ta’ Fuq) Kulur: beige ċar sa bajdani Proprjetajiet: ġebla tal-franka iebsa ħafna u kompatt Sinifikat: tifforma l-plateau stabbli fuq il-bajja. Meta s-saff tat-tafal ta’ taħt iċedi, il-blokki tal-ġebla tal-franka jinkisru u jiżolqu ’l isfel.
Blue Clay Formation (Formazzjoni tat-Tafal Blu) Kulur: griż sa griż-blu, iktar skur meta jkun imxarrab Proprjetajiet: impermeabbli, plastiku u faċilment deformabbli Sinifikat: kruċjali għall-pajsaġġ. Meta t-tafal jissatura bl-ilma, jitlef l-istabbiltà tiegħu, u dan iwassal għal żlielaq bil-mod u deformazzjoni plastika.
Globigerina Limestone (Ġebla tal-Franka Globigerina) Kulur: isfar ċar sa okra Proprjetajiet: ġebla tal-franka ratba u fina, li fiha fossili
Sinifikat: tifforma l-bażi tar-rdumijiet u hija parzjalment esposta fil-livell tal-bajja.
Il-Proċessi Ġeoloġiċi li Qed Jaħdmu
Dan is-sit huwa ffurmat prinċipalment minn moviment tal-massa aktar milli mill-erożjoni kostali klassika kkawżata mir-riħ jew mill-mewġ.
Saffi ta’ ġebla tal-franka iebsa jinsabu fuq saff ta’ tafal artab. Meta t-tafal jissatura bl-ilma, jibda jiċċirkola bil-mod ’l isfel taħt il-piż tal-blat ta’ fuq. Dan il-proċess jipproduċi: għoljiet ondulati u li jidhru qishom qed jiċċirkolaw, xquq ta’ tensjoni, tarġiet żgħar, żoni mxarrba fejn l-ilma joħroġ bil-mod.
Dawn il-proċessi għadhom għaddejjin, u jagħmlu l-għolja karatteristika ġeoloġika dinamika li qed tevolvi kontinwament.
Ir-Rwol tal-Ilma
Il-Maltemp
Il-maltemp jidħol fis-saffi ta’ ġebla tal-franka ta’ fuq u jilħaq it-tafal blu denses ta’ taħt. Dan jikkawża li t-tafal jassorbi l-ilma, isir iktar piżuż u jitilfu l-qawwa, u b’hekk jibda jiddeforma u jiċċaqlaq ’l isfel fuq l-għolja.
Il-Ilma tal-Baħar
L-iffju tal-melħ u l-umdità tal-ilma tal-baħar jidħlu fis-saff superficjali permezz tal-azzjoni kapillari, u jagħmlu ċertu partijiet mit-tafal dejjem mxarrba. Matul il-kosta, l-effetti magħquda tal-maltemp u tal-ilma tal-baħar joħolqu żoni kostanti mxarrba li jnaqqsu aktar l-istabbiltà tal-għolja.
SORSI
https://continentalshelf.gov.mt/geological-survey/geological-map/?utm_source=chatgpt.com, https://era.org.mt/topic/maltese-landscapes-geomorphology/?utm_source=chatgpt.com, https://era.org.mt/wp-content/uploads/2019/05/Rdumijiet_GhajnTuffieha_ManagementPlan.pdf?utm_source=chatgpt.com
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