ESTUARIES

The great Flandrian flooding

Around 15,000 years ago, the climate started to warm and then moved into the current interglacial period. Sea levels, which were about 120 m lower, began to rise to their present position about 5,000 years ago. This rise is clearly captured in the sediments of the Cantabrian estuaries.

Sand and silt boreholes

Around 30 metres of sand and silt sediment has been deposited in our estuaries over the last 10,000 years. Studying it helps us to understand how the great Flandrian transgression unfurled.

(Chart)

• Legends
  • Vegetable matter
  • Gravel
  • Muddy sands
  • Bioclasts
  • Black flysch
• X-axis: Deba borehole
• White column: 3,000-9,500 years
• Blue column:
  • Stabilisation
  • Slow rise
  • Rapid rise in sea level
• Right column:
  • Current estuary
  • Growing marine influence
  • Fluvial influence

(Left panel)

Rise in the sea level

An analysis of the estuaries has allowed us to determine the rate at which the sea level has risen over the last 12,000 years. Up to 7,000 years ago the sea rose by 10 mm/year. It became stable around 5,000 years ago at its present position and in recent decades has started to rise again by 3 mm/year.

(Left picture)

• 20,000 years ago

(Right picture)

• Current estuary
• 5,000 years ago
• Rise in the sea level
• 20,000 years ago

(Chart)

• X-axis: Sea level
• Y-axis: Geoparkea estuaries / Thousands of years
• Dashed line: Present day
• Blue areas:
  • 10 mm / year
  • 0.5 mm / year
  • 3 mm / year
  • Current level