5.10 Erosions
The rising of the tide can easily destroy a sandcastle on a beach. the ebb and flow of the waves pulls the grains of sand in the castle, until the whole structure disappears. this is a perfect example of erosion.
What is erosion?
earth’s crust is constantly being shapes by different forces that cause erosion.
Definition of erosion: erosion is the wearing away and transformation of soil and rock by glaciers, running water and weather (rain, wind, freezing and thawing).
Erosion of the Laurentides
the Canadian shield is the remains of a huge mountain range called the “Laurentides”. the laurentides were as tall as the Himalayas 1 billion years ago.
the Himalayas’ current peak (Everest) is 8848 metres high while the Laurentides’ peak (Mont Raoul-Blanchard) is 1181 metres high.
rain, running water and wind have crumbled rock and significantly eroded the Laurentides over time. a major ice age also contributed to the erosion; the slow movement of several kilometre-thick glaciers did much to wear away the rock.
Other examples of erosion
Niagara falls, which sits across the united states-canada border and extends to ontario, is receding by 30 centimetres per year. this happens because the fast moving water is eroding the rocks below.
The vermillion cliffs in Arizona are also an example of erosion because they were sculpted by the wind and the water.
the last example of erosion is the mingan archipelago in Québec’s côte-nord, it is made of ancient rocks. they were sculpted by the sea’s waves, which eroded softer rock and left harder rock behind. other eroding forces such as wind, freezing and thawing, continue to wear away at the rocks.
How are caves formed?
on the coast, waves crumble rocks by repeatedly smashing against them . farther inland, running water is a more common erosive force. it gradually dissolves and carries away the minerals in rock, sometimes bringing these into an underground river. either way, water is responsible for carving out the formations and hollow spaces inside caves.