Varve

Varve
Bayanai
Ƙaramin ɓangare na	stratum (en)
Fuskar	Quaternary geology (mul)

Ruwan tafkin glacial na Pleistocene a Sandend Bay a Scotland

A Varve ne shekara-shekara Layer na sedimentary ko sedimentary rock.

Kalmar 'varv' ta samo asali ne daga kalmar Yaren mutanen Sweden varv wanda ma'anoni da ma'anoninsa sun haɗa da 'juyin juya hali', 'a cikin yadudduka', da 'zagaye'.

Daga cikin rhythmites da yawa a cikin rikodin ilimin ƙasa, varves suna ɗaya daga cikin mafi muhimmanci da haskakawa a cikin nazarin Canjin yanayi na baya. Varves suna daga cikin ƙananan abubuwan da aka gane a cikin stratigraphy.

Layer na shekara-shekara na iya zama sosai ganuwa saboda barbashi da aka wanke a cikin Layer a lokacin bazara lokacin da ƙarfin kwarara ya fi girma fiye da waɗanda aka ajiye daga baya a cikin shekara. Wannan yana samar da nau'i-nau'i-nau'i-nau'i guda ɗaya kuma ɗaya mai kyau-na kowace shekara. Varves suna samuwa ne kawai a cikin ruwa mai laushi ko maras nauyi, saboda yawan gishirin da ke cikin ruwan teku na al'ada yana sa yumbu ya zama babban hatsi. Tunda ruwan gishirin yana barin ɓangarorin ɓarke duk shekara, kusan ba zai yuwu a bambance kowane yadudduka a cikin ruwan gishiri ba. Lallai, ƙwanƙolin yumbu yana faruwa a babban ƙarfin ionic saboda rugujewar laka mai ninki biyu na lantarki (EDL), wanda ke rage ƙwanƙwasa wutar lantarki tsakanin ɓangarori da aka yi cajin yumbu mara kyau.

Magana

Kalmar 'varv' ta samo asali ne daga kalmar Yaren mutanen Sweden varv wanda ma'anoni da ma'anoninsa sun haɗa da 'juyin juya hali', 'a cikin yadudduka', da 'zagaye'. Kalmar ta fara bayyana a matsayin Hvarfig lera (layyar yumɓu) a taswirar farko da binciken ilimin ƙasa na Sweden ya samar a 1862. Da farko, "varve" yana nufin kowane bangare daban-daban wanda ya ƙunshi Layer ɗaya na shekara-shekara a cikin tafkin glacial, amma a 1910 Geological Congress, masanin ilimin ƙasa na Sweden Gerard De Geer (1858-1943) ya ba da sabon ma'anar tsari, inda varve ke nufin duk wani Layer na shekara-mako. Kwanan nan an gabatar da kalmomin kamar 'a kowace shekara' daidai ne da varve.

Tarihin binciken varve

Varves a cikin wurin shakatawa a Itu, Brazil

Kodayake ba a gabatar da kalmar varve ba har zuwa ƙarshen ƙarni na sha tara, manufar sautin shekara-shekara na saukowa akalla ƙarni biyu ne. A cikin shekarun 1840, Edward Hitchcock ya yi zargin cewa laminated sediment a Arewacin Amurka na iya zama na yanayi, kuma a cikin 1884 Warren Upham ya yi ikirarin cewa haske-duhu laminated couplets wakiltar shekara guda. Duk da wadannan yunkurin da suka gabata, babban majagaba da kuma shahararren binciken varve shine Gerard De Geer. Yayinda yake aiki don binciken ilimin ƙasa na Sweden, De Geer ya lura da kamanceceniya ta gani tsakanin abubuwan da ke cikin taswirar da yake tsarawa, da zoben itace. Wannan ya sa ya ba da shawarar cewa ƙananan ma'aurata da ake samu akai-akai a cikin datti na tabkuna masu dusar ƙanƙara sune yadudduka na shekara-shekara.

De Geer ne ya gina jerin lokuta na farko a Stockholm a ƙarshen karni na 19. Ba da daɗewa ba aka ci gaba da aiki, kuma an kafa cibiyar sadarwar shafuka a gabashin gabar Sweden. Ruwan da aka fallasa a cikin waɗannan shafuka sun samo asali ne a cikin yanayin glaciolacustrine da glacimarine a cikin kwandon Baltic yayin da takardar kankara ta ƙarshe ta koma arewa. A shekara ta 1914, De Geer ya gano cewa yana yiwuwa a kwatanta jerin varve a fadin nesa mai tsawo ta hanyar daidaita bambance-bambance a cikin kauri, da kuma alamun laminae. Koyaya, wannan binciken ya jagoranci De Geer da yawancin abokan aikinsa cikin yin daidaituwa mara kyau, wanda suka kira 'haɗin kai', tsakanin nahiyoyi, tsarin da wasu majagaba kamar Ernst Antevs suka soki.