Sakawa Geology Museum And Institute

Geo Fantasy Room

Geo Fantasy Room

Japan Geology Map

How Japanese Archipelago formed.

Image of accretionary complex

 The surface of Earth is made up of plates, or giant bedrocks, which move very slowly against one another.  Japanese archipelago has mainly been formed of deposits of accretion brought by the movement of oceanic plate and sediments derived from the continent.  This accretion is made up of Oceanic sediments that have been scraped off and added to an archipelago arc or continental margin as the oceanic plate is slowly being pushed down under the Eurasian plate. Thus Japan Archipelago has made up of the mixture deposits of land-and ocean-derived sediments.
In accordance with this development, the formation of bedrocks of Japanese Archipelago generally becomes younger towards Pacific Ocean side rather than that of towards the Sea of Japan side.

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@ As Oceanic plate slides under the Continental plate, great volumes of eroded sediments from the Continent fall into the trenches of the subduction zone. However, some of those materials are not taken under the continental plate; rather, they are bulldozed back onto the continental shelf, further adding to the eclectic debris off-scraped from the ocean floor. Thus the accretion developed into a landmass which formed during Jurassic and Cretaceous periods (200 to 65 million BP). In these early stage, the landmass was mostly a continental margin (like the Andes of South America).

A The Archipelago was not formed until the expansion of today’s sea of Japan, during the Miocene epoch (between 25 & 15 million BP). Those islands bear little resemblance to that of those day.

B 21 millions to 11 millions years ago Japanese Archipelago twisted about 45 degrees clockwise and counterclockwise around at Itoigawa-Shizuoka Tectonic Line. Therefore, Northwest of Japanese archipelago formed narrow toward north and Southwest of it became narrow toward west.

C About 15 millions years ago, the big basin gradually formed between Japanese Archipelago and the Continent and sea water intruded into it and formed Japan Sea. In this way at the end of Cenozoic period (5.5 millions years ago) bow-shaped Japanese Archipelago had begun to form today’s shape vaguely.

D Japanese Archipelago connected with the continent again for sometime during Ice age After the last Ice Age was over, Soya strait, which separates Hokkaido and Honshu, appeared during the beginning of Holocene (13,000 BP). During this period Japanese archipelago was detached completely from the continent and probably formed today’s shape.

Now let us turn our eyes to Sakawa

There are many different geologic formations from Silurian through Cretaceous distributing in such a small area of Sakawa. Sakawa is therefore a very important municipality where earth scientists visit to research various strata and formations.
There are 3 criteria formations named after Sakawa’s place such as “Zohoin” formation (Middle Triassic), “Kochigatani” formation(Late Triassic) and “Torinosu” formation(Late Jurassic and Early Cretaceous) to compare the various formations of Cenozoic era of Japan.

Dinosaur Eggs & Thigh Bone
  Eggs of Dinosaur
 Thigh bone of Diplodocus
(Herbivorous Dinosaur)

Fantastic stones
Then, with the UV lights irradiating
from the lamp, they irradiate to deepen
its color in green, pink and purple.

Limestone fossils in Kochi

Environment on earth
In a bit to raise environmental consciousness and getting people to know much more about the Earth’s present state, this corner enlightens us what we should do to keep earth’s environment clean and beautiful.

・Influence of Global warming and Acid Rain.

・Dinosaurs time charts show you how they evolved.

・Chronicle of creature’s evolution
. From the Big Bang through current creature’s evolution.
・Fossils of various dinosaurs.
 Dinosaur’s egg, Fangs of Mosasaurus, Thigh bone of Diplodocus.

・Exhibition of limestone in Kochi prefecture.
・Torinosu limestone etc.
 Skelton of a false killer whale.

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Sakawa Geology Museum And Institute Ko 360 Sakawa-cho Takaoka gun Kochi ken, Japan :Zip code 789-1201

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