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.
Welcome to Qarraba Bay, a secluded coastal spot in north-west Malta!
Here you can observe how mud cracks form as the clay dries, how cycles of wetting and drying influence the cracks and slope stability. Practice careful observation and interpretation of geological features.
Log conditions and complete the task on site.
Observe the mud cracks from the listing coordinates and answer the following questions.
Question 1:
Describe the shape and pattern of the mud cracks.
Question 2:
Which geometric shapes are most prevalent, and what do this reveal about the drying process?
Question 3:
In what ways does the appearance of the surface differ between shallow and deep cracks, and what might these differences suggest about the drying process or the properties of the clay?
📸 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!
Geological background:
The blue clay mainly consists of clay minerals such as illite and montmorillonite, which often contain iron, magnesium and trace elements. Its blue colour is due to redox processes involving iron in different oxidation states.
These soft, highly erodible clay deposits form interesting structures and layers that record the sedimentation history.
Formation of mud cracks
These cracks appear when the fine-grained blue clay dries out during the hot summer months. As the water evaporates, the clay shrinks because the clay minerals lose volume when they lose moisture. This contraction creates tension in the surface layer, which is released through the formation of polygonal cracks.
The patterns reflect the natural stress distribution in the shrinking clay.
Impact of Rainfall
When it rains again, water quickly seeps into the cracks and soaks the clay layers. This rehydration softens the previously hardened clay, reducing its shear strength. As the clay is buried beneath a harder limestone cap, this creates a weak zone that is susceptible to small landslides or slope movements.
Repeated cycles of drying and wetting reshape the landscape over time, influencing both slope stability and local erosion processes along the coast.
Picture: AI
Surface cracks
These cracks are flat and fine. The clay surface remains mostly even, with only the lines of the cracks visible. Patterns can be seen, but the surface itself is smooth and continuous. Such cracks often form during slow drying or in clays with a low shrinkage rate.
Deep cracks
The cracks extend deeply into the clay layer. The blocks between the cracks may sink, tilt or break. The surface appears uneven, rugged and irregular. Deep cracks occur as a result of rapid drying, high shrinkage or repeated drying and wetting cycles. After rain, the surface may swell slightly, but the deeper cracks remain visible and shape the topography.
SOURCES
https://en.wikipedia.org/wiki/Mudcrack
https://era.org.mt/topic/maltese-geology/
Banner:AI & Sawi52
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.
Segwi t-tirqiq tal-ħamrija mill-koordinati tal-listing u wieġbu għall-mistoqsijiet li ġejjin.
Mistoqsija 1:
Iddeskrivi l-forma u l-patturn tal-qtar tal-ħamrija.
Mistoqsija 2:
Liema forom ġeometriċi huma l-iktar prevalenti, u x’juri dan dwar il-proċess tat-tnixxif?
Mistoqsija 3:
F’liema modi jidher is-superfiċje differenti bejn tqaxxir shalllow u tqaxxir profond, u x’jista’ jissuġġerixxi dawn id-differenzi dwar il-proċess tat-tnixxif jew il-proprjetajiet tal-ħamrija?
📸 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!
Sfondo Ġeoloġiku
Il-ħamrija blu tipproċedi prinċipalment minn minerali tal-ħamrija bħal illite u montmorillonite, li spiss fihom żejt, magniżju u elementi f’traces. Il-kulur blu tagħha huwa minħabba l-proċessi redox li jinvolvu l-azzar f’diversi stati ta’ ossidazzjoni.
Dawn id-depożiti artab u faċilment erodibbli joħolqu strutturi u saffijiet interessanti li jirreġistraw l-istorja tas-sedimentazzjoni.
Formazzjoni tat-Tirqiq tal-Ħamrija
Dawn it-tirqiq jidher meta l-ħamrija blu fina tinxef matul ix-xhur sħan tas-sajf. Hekk kif l-ilma jevapora, il-ħamrija tinżel għax il-minerali tal-ħamrija jonqsu fil-volum meta jitilfu l-umdità. Din il-kuntrazzjoni toħloq tensjoni fis-saff ta’ fuq, li tiġi rilaxxata permezz tal-formazzjoni ta’ tqaxxir poligonali.
Il-patturni jirriflettu d-distribuzzjoni naturali ta’ stress fil-ħamrija li qed tinżel.
Impatt tal-Maltempata
Meta tibda tinħela xita, l-ilma jidħol malajr fit-tirqiq u jinħall fis-saffijiet tal-ħamrija. Din ir-riidratazzjoni tassorbi l-ħamrija li kienet diġà kkapparata, u tnaqqas is-saħħa tas-shear tagħha. Hekk kif il-ħamrija tkun mgħottija taħt saff iktar iebes tal-ġebla tal-limestone, dan joħloq żona dgħajfa li tista’ tkun suxxettibbli għal żgħar ta’ fran jew moviment tas-saffijiet.
ċikli ripetuti ta’ tnixxif u umdità jirriformaw il-pajsaġġ maż-żmien, u jaffettwaw kemm l-istabbiltà tas-saffijiet kif ukoll il-proċessi lokali ta’ erosjoni ħdejn il-kosta.
Picture: AI
Tirqiq tal-Wiċċ
Dawn it-tirqiq huma ċatti u fina. Is-superfiċje tal-ħamrija tibqa’ prinċipalment livellata, b’ħafna linji tat-tirqiq viżibbli biss. Jistgħu jidhru patturni, imma s-superfiċje nnifisha hija lixxa u kontinwa. Dawn it-tirqiq spiss joħorġu waqt tnixxif bil-mod jew f’ħamrija b’rata baxxa ta’ kuntrazzjoni.
Tirqiq Profonda
It-tirqiq jespandi fondamentali fil-livell tal-ħamrija. Il-blokki bejn it-tirqiq jistgħu jinżlu, jitlefnu jew jinkiseru. Is-superfiċje tidher mhux livellata, ruwija u irregolari. It-tirqiq profondi joħorġu bħala riżultat ta’ tnixxif rapidu, kuntrazzjoni għolja jew ċikli ripetuti ta’ tnixxif u umdità. Wara xita, is-superfiċje tista’ tiżviluppa ftit, imma t-tirqiq iktar fondi jibqgħu viżibbli u jiffurmaw it-topografija.
SORSI
https://en.wikipedia.org/wiki/Mudcrack
https://era.org.mt/topic/maltese-geology/
Banner: AI & Sawi52
Editjar tat-test u traduzzjoni bl-għajnuna ta’ ChatGPT (reviżjoni minn Sawi52)
BANNER
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