Simplify the following text for a Grade 7 native English-speaking person.
Original: The lake reached 13 m long and over 100 metres in depth by the first week of June 2010 when it began flowing over the landslide dam , completely submerging lower Shishkat and partly flooding Gulmit .
Simplified: The lake reached 13 m long and over 100 meters in depth by the first week of June 2010 . At that time , it flowed over the landslide dam , completely submerging lower Shishkat and partly flooded Gulmit .