Really hoping somebody can help me with some subject knowledge of geology here. I'm a Primary School Teacher. Our topic is Mountains, with a focus on the Black Mountains in South East Wales (where we're going on residential in a few weeks). Last week we learned about Block Mountains, Dome Mountains, Fold Mountains and Volcanic mountains, and a basic description of how they are formed. Next week we are looking at the Black Mountains in particular. On doing my homework I find that the Black Mountains are made of Old Red Sandstone from the late Silurian and early Carboniferous and that the hills and valleys were shaped by glaciers from north Wales (which makes U shaped valleys?). As you can tell, my Geog knowledge in this area is sadly lacking. I understood that sandstones were formed at the bottom of the ocean (like limestone)... so how do they end up being hills? Do they form sandstone first, and then one of my folding/block/dome processes lifts them up? Does the weight of all that ice on the northern part of the landmass lift this end up? Or does the sea level drop so dramatically? As you can see I am really not the right person to be teaching this series of lessons, but I'm hoping that I can work it out and stay slightly ahead of the class!