the ground. Winds howl across mountain peaks and whistle through dark caves. Welcome to the wild, rocky Hebrides. Over


W


millions of years, wind, water, ice, and gravity have shaped these islands in Scotland. T ese forces of nature break apart and move rocks. T ey continually tear down Earth’s surface and build it back up again. T ese forces have sculpted a land so rugged


that no one can live on many of the islands. T ey’re a great place to visit, though. Here, we can hike across grassy highlands to jagged stone pinnacles. We can explore a fairyland of tiny hills. We can cross slippery cliff s, listen to musical caves, or picnic in a meadow. All of these wild places are diff erent. Yet


at each, we can see how wind, water, ice, or gravity have changed the land. Let’s explore.


Water at Work Our boat races to our first stop. Waves rock


it, and cold sea spray splashes our faces. Brrr! When we see where we’re going, we forget the cold. T e island ahead looks amazing, like it’s balancing on thousands of rock columns. As we float closer, we see a gaping hole in


the rock. It’s a cave. Inside, we hear a strange music. Flowing seawater gurgles and echoes as it slaps the cave walls. T e rushing water makes more than music.


It carves the cave. With each wave in, water seeps between cracks in the rock columns. Bit by bit, it chips away at the rock. It weathers the rock, breaking it into smaller pieces. With each wave out, the water erodes


the rock. It washes bits of rock out to sea. It deposits, or drops, the bits in a new place. Day by day, the cave slowly grows. Today,


its mouth reaches 22 m tall above our heads. It winds 82 m deep into the rock. Who knows how much bigger will it grow.


20 NATIONAL GEOGRAPHIC EXTREME EXPLORER


Ice Is Nice At another nearby island, we scramble to the


top of a cliff to look for puffins. Careful! T e sea spray makes the rocks slippery. Like in the cave, water wears away the rock


here. It changes the rock in another way, too. In winter, rain seeps into gaps in the rock. T e water freezes and expands. T e ice forces the gaps farther apart. T e ice eventually melts, but the bigger gap remains. T is series of events happens over and over.


Rain drips into gaps, turns to ice, and pushes the rock farther apart. Eventually, crack! T is cycle of physical weathering breaks the rock. Gravity helps, too. It tugs on cracked rock.


Broken bits tumble down the cliff s. Today, rocks that once topped the cliff now litter its base. Uneven rocks line the top of the cliff s T e seabirds that live here don’t mind that, though. All these broken rocks make perfect puffin perches.


aves crash against cliff s. Rain pounds


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