Atlas of Discoveries · 075V3 · Sonnet

Głodne Jeziorka · Drawa National Park

Lakes left by dead ice

From the trail you can see an oval water surface and a floating mat (pło). According to the description from Drawa National Park (DPN; to be verified), the small lakes lie in basins left by dead ice. That ice exists today only as a white outline of the reconstruction, and whether it was actually here is settled only by the sediments. Change the sediment data and see what changes in the result and what does not. Where do these descriptions come from?

Without JavaScript you see the default state: no sediment data and the outline of the ice mass. All four variants are described in the list in the section “The same shore, four answers”.

Schematic cross-section of a basin at Głodne Jeziorka Schematic, not to scale. Above the ground line only the water surface with floating mat at the edges and an observer on the trail are visible. Below the ground line the substrate is shown by hatching as unknown until you choose a data variant. The white, sparsely dotted outline around the basin is a reconstruction of the mass of dead ice. Default state: no sediment data, outline switched on as a hypothesis.
Above the ground line: visible from the trail.Below it: known only from boreholes and geological maps.Schematic, not to scale; not a map.

What do we know about the lake bed?

The view from the trail (A–C) does not change. Only what lies underground (D) changes, and whether the ice outline (E) has support.

Sediment data beneath the basin

Comparison result

Cannot be determined

Shape and vegetation are not enough. Without sediment studies the outline of the ice mass is only a hypothesis.

The result broken down into three layers of knowledge

Visible from the trail

An oval water surface, floating mat advancing from the shore, wooded shores, no surface outflow (descriptions from V2; DPN gives supply by precipitation and groundwater; to be verified). This view is the same in every variant: it does not distinguish the origin.

Requires sediment studies

Unknown. Hatching in the drawing means no data, not an empty layer or zero.

Reconstruction of the process

The outline of the ice mass is only a hypothesis. Without boreholes or a geological map it is not known whether there was any dead ice in this basin at all.

  1. viewpoint on the trail
  2. sphagnum floating mat
  3. water surface
  4. substrate: no data (hatching = unknown)
  5. outline of the ice mass: hypothesis without evidence (sparse dots)

Didactic diagram by the author of the page, without scale, dimensions or sounding of the lake bed. It is not a map or a surveyed cross-section. The depth of the basin, the thickness and the layer boundaries are unknown; the drawing gives no numbers.

Four steps of the reconstruction

This is a sequence of events, not a timeline. There are no years, melting rates or dimensions here: nobody has supplied them for any particular small lake. The white dotted outline marks ice that no longer exists.

  1. Step 1: burialDiagram: flat ground with a mass of ice buried in sediments below.
    1 · BurialA mass of dead ice remains in the channel, covered by sands and gravels carried by meltwater.
  2. Step 2: melting and subsidenceDiagram: a smaller mass of ice, with the ground above it subsiding.
    2 · Melting and subsidenceThe ice shrinks, and the sediments covering it lose support and subside.
  3. Step 3: empty basinDiagram: a dry basin in the sediments, with a dotted outline where the ice has disappeared.
    3 · Empty basinOnly the form remains. A basin alone does not guarantee a lake: without water it may remain a dry depression.
  4. Step 4: water and floating matDiagram: the basin filled with water, with floating mat at the edges.
    4 · Water and floating matPrecipitation and nutrient-poor groundwater fill the basin, and a floating mat advances from the shores. Today the history of the lakes continues as overgrowth.

The drawings are a general diagram of the mechanism described in PIG–PIB and DPN materials (see sources), not the history of any of the five small lakes. The steps share no time scale or dimensions.

The same shore, four answers

In all four entries the same thing is visible from the trail: an oval water surface with a floating mat. They differ only in what is known about the substrate. This list also works without JavaScript.

Limits of this page

Visible from the trail

  • an oval water surface and wooded shores,
  • floating mat advancing from the shore,
  • no surface outflow (description from V2; DPN gives supply by precipitation and groundwater).

Requires studies

  • type and arrangement of the sediments beneath the basin,
  • depth of the basin,
  • whether, and for how long, a mass of ice lay here.

What the page does not do

  • does not assess the certainty of the origin in percentages,
  • gives no dimensions or years,
  • does not indicate access to the water or the shores.

A floating mat is not a path. A floating blanket of plants may give way, and what lies beneath cannot be seen. Observe from the marked trail and check DPN notices on trail accessibility before setting out. According to the DPN guide, two of the five small lakes are visible from the blue trail (to be verified in the source).

What changed compared with V2

Field notebook removed
Saving in the browser was not needed to understand the topic, and it obscured the observation–interpretation pair. This version saves nothing; any old V2 entry in browser storage can be deleted in its settings.
Opacity slider replaced with two states
The outline of the ice mass is either on or off. Gradual revealing explained nothing.
Stage slider replaced with four static drawings
The four steps are visible at once, without simulating the passage of time.
Four lists of features replaced with a single sediment control
Shape, vegetation and water supply can be seen from the shore and do not distinguish the origin, so they changed nothing in the result. What remains is what actually decides: data on the substrate.
The Wikimedia Commons photograph is not embedded
The page works offline, so instead of the photograph there is its own diagram, and the photograph is only a link in the sources.
Kept
The breakdown of the result into “visible”, “requires studies” and “reconstruction”, the “cannot be determined” state, the prohibition on stepping onto the floating mat, and the source links.

Sources

Links carried over from V2. They were not opened or re-checked when this version was built, so content labelled “according to” needs confirming in the original.