This study examined whether junior high school and high school students can determine natural water inundation predisposing factors using GSI maps a web map developed by the Geospatial Information Authority of Japan （GSI）.　With a specific focus on the microtopography formed by rivers, students presented the susceptibilities of the 2019 floods of the Kuji River in Ibaraki Prefecture and the 2004 floods of the Maruyama River in Hyogo Prefecture, based on information on the causes of landform formation and elevation collected using GSI maps.　The results revealed that the majority of students were able to master the basic functions of the GSI maps, had the ability to make inferences based on geographic information and developed an understanding of the triggers of natural disasters and their susceptibility factors.　The students were apt to select a coloured contour map during the activity;however, they were unable to conduct a cross-section of geomorphology.　The reason for this result may be that the students lacked sufficient knowledge on topography.　Given their academic ability in terms of geomorphology, GSI maps are deemed beneficial to geography classes in Japan.

　　　Along the Yoshino coast, southeast of Miyako Island, several spring waters gush out from the lower part of the marine terrace cliff. Several stratified and cemented sand layers are observed at 1.5～2.0 m a.s.l. along the small streams of spring water.

　　　To obtain basic data related to the formation mechanism of cemented sand layer, hydrological analysis of spring water and measurements of radiocarbon concentration and δ¹³C value of cemented and un-cemented sand layers were carried out. The results are summarized as followings:

1） Spring water is classified into Ca-HCO₃ type, which indicates characteristic in other limestone area.

2） DIC (Dissolved Inorganic Carbon) of two spring water samples gave yielded values of 89.8±0.3 pMC and 89.3±0.3 pMC respectively. While DIC of cemented and stratified sand layer, and un-cemented lower sand layer indicated 84.1±0.3 pMC and 77.5±0.2 pMC.

3） The δ¹³C values of two spring water samples were －9.8‰ and －9.9‰, while those of the cemented sand layer, and lower un-cemented sand layer were －0.9‰ and +0.4‰, respectively.

4） The stratified and cemented sand layers were formed under the cementation of sand and CaCO₃ precipitated in the reverse reactions of the resolved limestone solution. The area of distribution, slope, hardness, superposition form, sedimentary facies and ¹⁴C age of the cemented sand layers differ from beachrock, eolianite and tufa.