Ancylus Lake = About 10,800 years ago, the straits of the Yoldi Sea were cut off from the ocean by uplift. The Ancylus Lake phase began in the Baltic Sea basin. Just over 10,000 years ago, the first stream of Ancylus Lake moved from central Sweden to what are now the Danish straits.
Baltic Ice Lake = The first and second Salpausselkä ridge systems were formed on the edge of the continental glacier, while it remained in the same area 12,300–12,100 and 11,800–11,600 years ago. At that time, by the glacier was the freshwater Baltic Ice Lake, which fallout to the ocean was located at the present-day Danish straits.
Baltic Sea phases = The ancient Baltic Sea includes the Baltic Ice Lake, the Yoldia Sea, Ancylus Lake and the Littoral Sea.
Beach mark = Different types of beach marks, which may be depositional or abrasive, are mainly the result of the action of waves, storms and coastal currents. Beaches are also shaped by ice movement and wind.
Breccia = A rock type with angular rock fragments in a younger rock type.
Cliff = Bank eroded by waves, most often created from sorted material.
Cordierite = A common mineral in gneisses and migmatites
Crushed zone = Fracture zone created by the release of internal stress in bedrock.
Deformation = An event in which displacements, abrasion zones, fissures, fractures and directional structures are created in rock by compressive and tensile forces.
Dike = The alveolar occurrence of the rock type. In dikes, magma is crystallised in cracks in the bedrock and sometimes the dikes cut sharply into other rocks.
Drumlin = A streamlined ridge formed by the movement of the continental glacier in the direction of the basal moraines.
Drumlinisation = A process in which the strong flow of a glacier causes to form moraine ridges at the base of the glacier.
Drumlin shield = A broad, usually rock-filled uplift, shaped in the direction of glacier movement, in which discrete drumlins can be distinguished.
Equigranular = a type of rock or soil composed of particular grain size.
Esker = A ridge or hummock formed by material (rocks, gravel, sand) carried by a glacial river.
Fault zone = A fracture surface or fault zone in the rock along which the displacement of one rock block relative to another has occurred.
Flakiness = A rock deformation with a planar structure. The rock is broken into flat pieces according to the flakiness.
Gabbro = Dark, alkaline intrusive rock type
Garnet = A group of silicate minerals with a rather complex chemical composition. Garnets are common in metamorphic rocks.
Giant's kettle = A hole or cavity in the rock carved out by meltwater and rock material from a glacier. River potholes form at the rapids of flowing waters.
Glacial erratic = A large boulder quarried and transported from a rock by a continental glacier. The boulders have been transported by flowing glacial ice or by an iceberg that has drifted in the water.
Glacial lake = In the Lake Saimaa area, the eruption of the Baltic Ice Lake was followed by a couple of centuries of glacial lakes. The local glacial lakes dammed up at the edge of the glacier and erupted when the melting glacier revealed depressions low enough to be covered by ice.
Glacial mark on rock = The direction of scratches and trough (furrow, trough, sickle trough, crescentic gouge, lunate mark, crescentic fracture) cut into the rock surface by the glacier.
Glacier river delta = A delta formed at the edge of a glacier, in front of a glacial river, where meltwater is deposited and sorted.
Gneiss = A structurally oriented, medium- to coarse-grained metamorphic rock, i.e. a rock formed by the metamorphism of another rock type.
Granite = Finland's most common rock type, the main minerals being potassium feldspar, plagioclase, quartz and mica. Granite is an intrusive rock, meaning that it has formed by crystallisation of melt deep in the Earth's crust.
Granodiorite = An intrusive rock whose main minerals are plagioclase, potassium feldspar and quartz, together with biotite and/or hornblende.
Highest coastline = The water level in the area when the land was exposed under the melting glacier. The highest coastline was formed in different areas at different times. This is because Southern and Eastern Finland were exposed before the rest of Finland. As a result of uneven upthrust, the highest coastlines of the same phase may be located at different altitudes. On ridges and marginal landforms, deltas that have risen to water level represent the highest coastline.
Ice sheet = A glacier is a continental glacier if its extent exceeds 50,000 km2. Finland was last covered by a continental glacier during the Vistula Ice Age, which ended around 11,000–10,000 years ago.
Igneous rocks = Rocks formed by crystallisation from molten rock.
Imatra stones = Chalk coagulates, formed in clay deposits of River Vuoksi area during the melting phase of the continental ice sheet. Imatra stones are protected and may not be collected and sold.
Intrusive rocks = Igneous rocks formed by crystallisation deep in the Earth's crust, e.g. granite and gabbro.
Kettle = A pothole or depression in the surface of a delta formed when a block of ice detached from the edge of a glacier first buried in sand layers and later melted.
Lake Saimaa phase = The Lake Saimaa phase was about 6,900 years ago, when the water level of lake basins was at the same level from South Karelia to North Karelia and North Savo.
Limestone (carbonate rock) = A metamorphic rock composed of calcite mineral. It is formed by the recrystallisation of calcareous matter precipitated and sedimented from seawater in the Earth's crust at high pressure and temperature.
Meta- = A prefix referring to metamorphism or metamorphosed rock.
Metamorphic rocks = Rocks whose structure and/or mineral composition has changed during the various stages of crustal evolution.
Metamorphism = A geological event in which the rock structure or mineral composition, or both, are altered by movement or changed temperature and pressure conditions.
Mica gneiss = Gneiss rich in mica
Mineral = A naturally occurring crystalline substance with a characteristic chemical composition. A mineral can also be formed by a single element.
Moraine = Composed of moraine, e.g. drumlins and marginal moraine beds and ridges.
Pegmatite = A very coarse-grained, semi-superficial igneous rock, i.e. formed by the erosion of magma in the upper parts of the Earth's crust. Pegmatites often occur in dike-like.
Phenocryst = A coarse mineral grain in a fine-grained matrix
Porphyry = fragmented igneous rock
Raised beach = The beach markers above the current shoreline are raised beaches.
Rapakivi granites = A group of granitic rocks crystallised near the surface of the crust. Rapakivi granites are the youngest rocks in our bedrock.
Rift = An elongated depression in a rock's fracture.
River delta = Delta of a river or glacial river, a formation of sorted material deposited by a river in water.
Roche moutonnée = A glacially eroded and abraded rock with a gently rising, rounded opposite side (glacier-facing side) and a steep, jagged protective side.
Rock types = Rock types composed of one or more minerals.
Sandur = A dry land delta, i.e. a delta that has risen above the water surface. On the surface of the sandur there are drainage nets along which the meltwater flowed.
Sedimentary rocks = The types of rocks formed as a result of the re-layering and hardening of weathering products.
Shorelevel displacement = The gradual movement of the shoreline of a sea or lake down or up a slope, either as a result of water level fluctuations, upthrust or land subsidence.
Stream bed = A river stream of a lake to the sea. For example, the Lake Saimaa stream bed is called Vuoksi.
Subglacial till = A dense, often fine-grained, unsorted soil formed at the base of a glacier.
Terminal moraine = A moraine ridge formed on the edge of a glacier, parallel to the edge of the ice.
Till = A mixed type of soil formed by the loosening and transport of rocks by glaciers, which may contain grain sizes ranging from clay to boulders. Moraine is the most common soil type in Finland.
Tirilite = A fayalite bearing, dark-coloured and even-grained variant of rapakivi granite. The name of this rock comes after its finding site, the Tirilä village of Lappeenranta.
Tonalite = An intrusive rock with only a few potassium feldspar minerals
Upthrust = During the Ice Age, a thick continental ice sheet pressed the crust of the Earth into dents. As the ice sheet melted, the crust began to return to its former position. In Finland, upthrust is fastest around the Bothnian Sea, where the glacier was thickest. As a result, the crust is tilted to the southeast. The tilting of the crust has had a decisive influence on the phases of Lake Saimaa.
Varved clay = Seasonal stratified clay transported and deposited by glacial meltwater. As the glacier melted more slowly in winter, thin dark layers formed, and as the melting accelerated in summer, thicker light layers formed.
Vein gneiss = Gneiss with abundant granitic veins
Viborgite = A rapakivi variety with pale plagioclase rings around the potassium feldspar phenocrysts (ovoids).
Volcanic rock = Crystallised lava that has erupted from a volcano. In Finland, old volcanic rocks have metamorphosed and are called metavolcanic rocks.
Yoldia Sea = Around 11,580 years ago, the Baltic Ice Lake opened up to the sea in central Sweden, causing the water level to drop by 26–28 m. The seawater flooded into the Baltic Sea basin, where the Yoldia Sea phase began. In the Lake Saimaa area, the eruption of the Baltic Ice Lake was followed by two centuries of glacial lakes. Yoldia Sea only spread into the geopark area as narrow bays about 11,400 years ago.