Gli endemismi vengono provocati solitamente da un certo tipo di isolamento. Gli esseri viventi possono essere isolati da diversi fattori.
Il più semplice da comprendere può essere la presenza di un braccio di mare o di una catena montuosa…
Ma anche l’esposizione ai raggi solari, ai venti, l’altitudine, il clima, la temperatura, la pressione, la limpidezza e la salinità dell’acqua (per gli organismi acquatici), insieme ad altri fattori (a volte anche comportamentali) possono determinare isolamento e la formazione di una nuova specie endemica o il mantenimento di un’antica specie solo in determinati luoghi ideali.
Le vediamo in questo articolo nel loro spiccato mimetismo con le rocce vulcaniche e in alcuni particolari in cui si notano le dimensioni degli esemplari, il tipico “collare”, gli artigli delle zampe anteriori e posteriori. le macchie laterali con la tipica colorazione e la loro bellezza esotica!!!
Qualche giorno fa, durante una bella giornata di arrampicata con l’amico Ingegnere, Geologo e Guest Blogger di scienzafacile, abbiamo parlato di Karren e così, Luca mi ha inviato delle belle fotografie di questi Campi Carreggiati (altro nome dei Karren!) Anche questi sono stati erosi anche se in modo meno importante rispetto a quelli che fogografai in Grignone!
Ora mancano solo quelli con le crestine iper-affilate che vuol dire che sono sottoposte a erosione da minor tempo…
Qualche giorno fa li ho visti in grotta a -80m ma per ragioni di riservatezza non posso illustrarveli.
Concludendo, durante la giornata abbiamo poi anche arrampicato per un attimo sui Karren sotto la pioggia e come affermato sul precedente articolo, la tenuta delle scarpette anche su questo particolare fondo bagnato è estremamente efficace!
Ecco qui i “Karren di Luca” visti da diversi angoli:
E’ una magnifica giornata d’estate. Mi reco al rifugio Bietti-Buzzi a trovare un’amica che poi invece non c’è!!! Quindi, dopo un bel piatto di pasta e una coca, attraverso la via dei Guzzi e la Cresta di Piancaformia (questi ultimi due, come molti altri sentieri delle Grigne, sono percorribili solo da Escursionisti Esperti!) salgo sulla Cima del Grignone dove si trova il Rifugio Brioschi.
Per la discesa percorrerò tutta la parte bassa della Cresta di Piancaformia in una serata calda e solitaria nonostante sia domenica…
La cresta si sviluppa quasi totalmente sui Calcari massicci di Piattaforma (vedi link) e in alcuni punti si incontrano i Karren, forme dovute alla dissoluzione della roccia ad opera dell’acqua piovana.
I Karren vengono scavati proprio dall’acqua piovana che diventa acida mischiandosi con i gas dell’atmosfera. Quando arriva a terra, l’acqua si mischia anche con gli acidi del terreno diventando più “aggressiva” e scioglie (nel vero senso della parola) il calcare.
La molecola del Calcare infatti, così come quella del Salgemma o Halite (che è il nome mineralogico del sale da cucina), può essere separata in due parti dall’acqua. Quando viene separata così, chimicamente, si dice che Leggi tutto “Erosione e dissoluzione!”
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