How do pebbles form > www.youtube.com/watch?v=8C7jnP4lt8w :
EPIC Pebbles : A story of continental COLLISION and VOLCANISM 5.20 easy guide.
Notes and quotes
Pebbles come from when the earth shifted, sedimentary rock, different colours describe the strata, Volcanic tectonic activity can move them into new position.
Pebbles and strata formed from the pressure of the magma and liquid forcing itself, and the heat changed the chemical makeup of the rock,.
In this example Dr Haydon Mort - Geologist from UFPE, Brazil discuss slate and strata that can be seen at Seaton in Devon( which was a surprise as it was the place where my father - a Geographer, taught me about rocks and geology.
Haydon discussed Slate, it's process of being a mud at the bottom of the sea floor and how with tectonic shifts , the pressure, and heat from the shifts changed it chemical compounds. Green/ Red colour is created through the different amounts of Iron oxide is at the bottom of the sea.
The whole set of rock formation has at 45 deg slant which means that this was moved by the tectonic plate activity.
These build up over 150 M years. The ocean closed and formed a massive mountain range, the same Volcanism created the body of the slate, the veins in the slate are calcium. Calcium rich magma mixed with the water to heat the rock so much that it changed the rocks chemistry. The shale turned into Slate.
Stretches back 400 m years.
Pebbles are created by the never-ending action of the waves as it ground and smoothed their edges. Similar rocks to these are evident also in Cornwall..
The pebbles become individual records of the continents colliding.
Easy reminder resource - simplified but gives basic threads: look into the geological rock formations of the South of Spain .