Final answer:
Chilled and baked margins are formed as the magma cools when intruding into country rock, with the result being varying crystal sizes in the final rock formed. Faster cooling at the outer layers (chilled margin) results in smaller crystal size, while slower cooling towards the center causes larger crystals.
Step-by-step explanation:
When magma intrudes into the crust, it heats up the surrounding rocks in a process called contact metamorphism. This process results in the creation of baked margins around the magma intrusion. On the other hand, the chilled margin is formed where the magma comes into contact with the cooler country rock, causing it to cool and solidify rapidly.
The size of crystals in intrusive rocks is directly related to the cooling rate of the magma. Faster cooling rates, such as those at the chilled margin, result in smaller crystals because there is less time for the ions to move and grow. Conversely, the center of the magma body cools slowly, allowing time for large crystal growth.
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