Beaches are natural geological formations that develop where a body of water meets the land. Beaches can be made of a variety of materials - sand and/or rock: silica or quartz and other hard materials: (gypsum, obsidian, coral, shells, and oolites).
What is sand?
Sand is a loose granular material blanketing the beaches, riverbeds and deserts. In different areas sand has different components which makes the sand white, black, green or pink in color.
Sand is mostly composed of silicon dioxide in the form of quartz. Quartz is hard and don't decompose easily.
The Earth's landmasses is composed of rocks and minerals, including quartz, feldspar and mica. Weathering processes like wind, rain and freeze/thaw cycles break these rocks and minerals down into smaller grains.
Unlike other minerals quartz is hard, insoluble in water and won't decompose easily from weathering processes. Streams, rivers and wind transport quartz particles to the seashore where the quartz accumulates as light-colored Beach Sand.
This beach is not very steep at the shoreline; this tells us that the water offshore is shallow. The waves that hit the shoreline carry sand and small rocks, which build up the beach and shape the coastline. Beaches on tidal waters will become sandy faster than those with no tides. The time between high and low tide is six hours apart and the tide cycle happens 50 minutes later each day.
Sand Source
By identifying the components of sand, it is possible to tell what the sand is made of. Sands can be broadly classified by their source into two types, biogenic sand and abiogenic sand. Biogenic (bio = living; genic = produced by) components are the living or once-living components of an environment. Abiogenic (a = not) components are the non-living chemical and physical components of an environment.
Abiogenic, or “lithogenic” (litho = stone), sand grains are formed as rocks break down through weathering and erosion. Erosion is the movement of weathered rocks and minerals from one location to another. Abiogenic sands can be formed from rocks in the continental crust or the oceanic crust of the earth. The continental crust includes most of the major landmasses of the world. Mountains in the continental crust are composed mostly of granite. Mineral sands formed by the breakdown of granite usually contain quartz, feldspar, mica, and magnetite. Minerals are solid, naturally occurring substances composed of a single chemical compound. For example, quartz is a mineral composed of the chemical compound silicon dioxide (SiO2).
Geology of the São Tomé
The entire island of São Tomé is a massive shield volcano that rises from the floor of the Atlantic Ocean, over 3,000 m (10,000 ft) below sea level. It formed along the Cameroon line, a line of volcanoes extending from Cameroon southwest into the Atlantic Ocean. Most of the lava erupted on São Tomé over the last million years has been basalt. You can see examples of basalt everywhere on the island.
As you visit this earthcache and walk along this beach you will notice that the waterline is almost fully covered with black rocks. Its a basaltic rock, which was formed when flowing lava hit the water and rapidly cooled down.
To log this cache.
To get to log this cache you will have to visit and answer the questions which are related to the coordinates given the earthcache.
When answers are collected, send them to CO for verification.
You can log immediately after answers are sent CO. If there are any questions about your answers CO will contact you.
Logs without answers to CO or with pending questions from CO will be deleted without any further notice.
Questions:
1. Answer the questions under by visiting the given Coordinates.
A. What type of beach this is: Abiogenic or Biogenic or maybe both? Justify your answer
B. Take the sand in your hand. Tell me what is the mineral composition of this sand?
C. What is the average grain size of the sand? Does the size changes, if you compare sand close to water with sand few meters away from water?
2. Take a photo of you (face showing is not mandatory) or a personal item from the location without revealing answers.
If you visit this cache as "team", your cache log needs to be attached with individual photo. Logs with the same photo for all "team" members are not permitted.
Enjoy the beach and have fun.
Happy Caching!