I am the official currency of a nation renowned for its glaciers, volcanoes, and geothermal activity. My name echoes a historical weight and a legendary metal. I am independently managed and not pegged to any other currency. What currency am I?

1. My value has historically been affected by fluctuations in fish stock yields.
2. My central bank is called the 'Seðlabanki'.
3. A famous saga involves a character named 'Egill Skallagrímsson' who was concerned with the value of this currency in silver.
4. Picturesque waterfalls and the Northern Lights are often associated with my homeland.