There are three main types of rocks - Igneous Rocks, Sedimentary Rocks and Metamorphic Rocks.
Igneous rocks are formed when magma (molten rock within Earth's crust and upper mantle) cools and hardens, this process is called crystallisation or solidification. Igneous rocks may form either beneath the surface or at the surface through volcanic eruption. Some igneous rocks looks shiny and glasslike. However, sometimes gas bubbles are trapped in the rock during the cooling process and leaving tiny holes and spaces in the rock.
Sedimentary rocks are formed when sediment (from igneous rocks through weathering and erosion, shells, sand and other fragments of materials) get compacted or cemented together. This process is called lithification, a term meaning "conversion into rock". Generally, sedimentary rock is fairly soft and may break apart or crumble easily. You may see sand, pebbles, or stones in the rock, and sedimentary rock is usually the only type of rocks that contains fossils.
The Metamorphic rocks get their name from "meta" (change) and "morph" (form). If a sedimentary rock becomes deeply buried or is involved in the dynamic of mountain building, it will be subjected to intense temperature and pressure. The changing environment makes the minerals in the rock becomes unstable and out of equilibrium and turning into metamorphic rocks. Metamorphic rocks often have ribbon-like layers and may have shiny crystals, formed by minerals growing slowly over time on their surface.
If metamorphic rock is subjected to a much higher temperatures, it may melt and create magma. Therefore, the rock cycle begins again!
EarthCache Task
I hope that the paragraphs above could gives you some basic understandings and features of rocks. These information may help you to complete the EarthCache task. My aim is to generate your interest in geology and earth science. You may also want to do some further studies and research before or after EarthCaching.
At the given coordinates you will find the target rock. In order to prove your visit and claim the find, please email me with the answers to the below listed questions. Please take a photo of yourself/selves through the structure or riverside in the background. Although the there is a platform around the GZ, please be careful of your geo-kids and be sure to judge the conditions on the day yourself.
Once I receive your answers and I get back to you, you may log your find & attach the photo you took. Hope you enjoy the EarthCache and the "Introduction to Rocks 101".
Questions:
- What type of rock is it? Igneous, Sedimentary or Metamorphic?
- What can you see on the surface of the rock and why did it happen?
Bonus question: (not a requirement for the Earthcache)
3. What is the rock called specifically?