Breg Save
Povirje Save leži v celoti v Sloveniji, njenemu porečju pripada več kot polovica slovenskega ozemlja. Ima dva povirna kraka, vendar navadno štejemo Savo Dolinko kot njen glavni krak. Izvira v Zelencih pri Podkorenu, teče proti vzhodu in jugovzhodu ter se pod Radovljico združi s Savo Bohinjko, ki priteka iz Bohinjskega jezera. Združena reka nadaljuje svoj tok po Ljubljanski kotlini, se v ozki soteski prebije skozi Posavsko hribovje, prečka Krško kotlino in pod Brežicami vstopi v Panonsko nižino. Večinoma teče po široki dolini po njenem južnem robu in se pri Beogradu izlije v Donavo.
Skrilavec
Skrilavec je metamorfna kamnina, ki vsebuje različne minerale. Njegova posebnost je, da ga je mogoče cepiti na ploskve, zato se je včasih veliko uporabljal v gradbeništvu.
Določa ga več kot 50% ploščatih in podolgovatih mineralov, pogosto fino prepletenih s kremenom in glinencem. Te luske mineralov vsebujejo sljudo, klorit, lojevec, rogovačo, grafit in druge. Pogosto se pojavlja kamena strela , zato se ta posebna oblika imenuje kremenov skrilavec. Skrilavec ima pogosto granate. Skrilavec se je oblikoval pri višji temperaturi in ima večja zrna kot fillit. Geološka foliacija (plastnata tekstura metamorfnih kamnin, ki vsebujejo listaste silikate) s srednje velikimi zrnatimi kosmiči v želeni listni usmerjenosti, se imenuje schistosity. Imena različnih skrilavcev izhajajo iz njegovih mineralnih sestavin. Na primer, skrilavec bogat s sljudo se imenujejo sljudni skrilavec in vsebuje biotit ali muskovit. Večina skrilavcev so sljudni skrilavci, pogosta pa sta tudi grafitni in kloritni skrilavec. Skrilavec so poimenovali tudi po njegovi poznanosti ali morda nenavadnih mineralnih sestavinah, kot je primer granatni skrilavec, turmalinov skrilavec in glaukofanov skrilavec.
Posamezna mineralna zrna v skrilavcih, razvlečenega v luske s toploto in pritiskom, je mogoče videti s prostim očesom. Skrilavec je značilno plastnat, kar pomeni, da se posamezna mineralna zrna z lahkoto odcepijo v kosmičih ali ploščah. Beseda skrilavec izhaja nenazadnje iz grške besede schízein in pomeni 'razdeliti', kar se nanaša na enostavnost, s katero se skrilavec lahko razdeli v ravnini, v kateri ležijo ploščati minerali.
Vprašanji:
1. Poglej kamen, ali potekajo plasti skrilavca vodoravno ali navpično? Zakaj mislite, da je tako?
2. Poglej kamen ali je lahko lomljiv, glede na to kar vidiš? Ali se ti zdi, da je lomljiv v vse strani enako ali se lažje lomi po plasteh, glede na to kar vidiš?
Neobvezno:
1. Vpisu lahko priložite tudi fotografije.
Sava Riverbank
The Sava is a river in Central and Southeastern Europe, a right tributary of the Danube. It flows through Slovenia, Croatia, along the northern border of Bosnia and Herzegovina, and through Serbia, discharging into the Danube in Belgrade. Its central part is a natural border of Bosnia-Herzegovina and Croatia. The Sava forms the northern border of the Balkan Peninsula, and the southern edge of the Pannonian Plain.
What is Schist?
Schist is a medium-grade metamorphic rock with medium to large, flat, sheet-like grains in a preferred orientation - nearby grains are roughly parallel. It is defined by having more than 50% platy and elongated minerals, often finely interleaved with quartz and feldspar. These lamellar minerals include micas, chlorite, talc, hornblende, graphite, and others. Quartz often occurs in drawn-out grains to such an extent that a particular form called quartz schist is produced. Schist is often garnetiferous. Schist forms at a higher temperature and has larger grains than phyllite. Geological foliation with medium to large grained flakes in a preferred sheetlike orientation is called schistosity.
The individual mineral grains in schist, drawn out into flaky scales by heat and pressure, can be seen with the naked eye. Schist is characteristically foliated, meaning that the individual mineral grains split off easily into flakes or slabs. The word schist is derived ultimately from the Greek word σχίζειν (schízein) meaning "to split", which is a reference to the ease with which schists can be split along the plane in which the platy minerals lie.
Most schists are derived from clays and muds that have passed through a series of metamorphic processes involving the production of shales, slates and phyllites as intermediate steps. Certain schists are derived from fine-grained igneous rocks such as basalts and tuffs.
During metamorphism, rocks which were originally sedimentary, igneous or metamorphic are converted into schists and gneisses. If the composition of the rocks was originally similar, they may be very difficult to distinguish from one another if the metamorphism has been great. A quartz-porphyry, for example, and a fine grained feldspathic sandstone, may both be converted into a grey or pink mica-schist. Usually, however, it is possible to distinguish between sedimentary and igneous schists and gneisses. If, for example, the whole district occupied by these rocks has traces of bedding, clastic structure, or unconformability, then it may be a sign that the original rock was sedimentary. In other cases intrusive junctions, chilled edges, contact alteration or porphyritic structure may prove that in its original condition a metamorphic gneiss was an igneous rock.
The schists are classified principally according to the minerals they consist of and on their chemical composition. For example, many metamorphic limestones, marbles, and calc-schists, with crystalline dolomites, contain silicate minerals. They are derived from calcareous sediments of different degrees of purity. Another group is rich in quartz. The graphitic schists may readily be believed to represent sediments once containing coal or plant remains; there are also schistose ironstones, but metamorphic beds of salt or gypsum are exceedingly uncommon.
Questions:
1. Look at the stone, are the layers of shale horizontal or vertical? Why do you think that is so?
2. Look at the stone. It look fragile, acording to that what you see? Does it seem that it is fragile in all directions in same way, or is it breaking in layers, depending on what you see?
Optional:
1. You can make some photos and add them to your log.