Tal-y-llyn Lake - Tywyn

Tal-y-llyn Lake, also known as Talyllyn Lake, Llyn Mwyngil or Llyn Myngul is a large glacial ribbon lake in Gwynedd. It is formed by a post-glacial massive landslip damming up the lake within the glaciated valley. Tal-y-llyn Lake is situated to the north of Machynlleth, at the foot of Cadair Idris, in the Snowdonia Mountain range. The River Dysynni flows from the lake, through the village of Abergynolwyn, and discharges into the sea north of Tywyn.

There is a route leading to the summit of Cadair Idris from near the lake and the narrow gauge Talyllyn Railway has its eastern terminus at nearby Abergynolwyn.

The Tal-y-llyn Lake is located on a major fault line in Wales known as the Bala Fault, which extends from the Cheshire border to Towyn on the Cardigan Bay coast. The depression caused by this was likely carved out and deepened during subsequent glaciation periods. Until 1962, Tal-y-llyn Lake was regarded as the most southerly example of a lake formed in a rock basin, with a terminal moraine on top of the bedrock through which the river had carved a channel. It is now understood that what appeared to be bedrock is in fact massive blocks of debris left by a large landslide. An