1. Intrusive Landforms Intrusive Landforms: Intrusive Landforms are formed by magma rising towards the surface but cooling and solidifying before being extruded.

2. This is likely to be the case if… If magma is rising slowly. If there is a great thickness of crust to pass through. Few weaknesses in the crust through which it can flow out.

3. Why does the magma cool so slowly? Because it is not exposed to the air… …and so mineral crystals (quartz in granite) grow to a large size. Types of Intrusive Landforms Batholiths Bosses Sills Dykes / Dikes

5. Batholiths Large masses of intrusive rock. Cause a general doming up of the surface as they are forming. Only exposed after general weathering and erosion of less resistant overlying ‘country rock’. Weathering is facilitated, (helped), by the fractures and cracks that develop due to the tensional forces that develop the surface experiences as it is stretched during uplift. Similar but smaller features are known as Bosses (Shap in Cumbria).

6. Batholiths continued…. The heat / pressure exerted on the country rock causes metamorphic rock to be produced around the intruding magma. An example of this is sandstone being metamorphosed into schists and limestone into marble. Metamorphic Rock = Rocks that have been changed from their original form by heat or pressure beneath the surface of the earth.

7. Sills Intrusions formed parallel to bedding planes in country rock, often, but not always, lying horizontally. The bedding planes provide a line of weakness along which the magma will flow before cooling and solidifying. The magma contracts as it cools, producing cracks in the resultant rock. When the overlying rock is weathered and eroded the sill is exposed. Sometimes these exposed sills form steep coastal cliffs or rock outcrops, including cap rocks on waterfalls.

8. Dykes (Dikes) Dykes cut across the bedding planes of country rock often vertically. Magma flows through cracks and weaknesses but again cools and solidifies before reaching the surface. Contraction joints develop parallel to the surface as the magma solidifies. Once exposed, Dykes can appear as linear outcrops of resistant rock.

9. An Exposed Dike in New Mexico