This plateau has hills and hillocks covered by grasslands, known as coxilhas, whose highest levels do not exceed 600 metres in altitude. This plateau was formed in Precambrian time, divided by the Camaquã River in two main units, Serra de Herval and Serra dos Tapes. This region has a triangular area between the cities of Porto Alegre, Jaguarão and Dom Pedrito, approximately. It is an old plateau, whose tabular relief is preserved only in areas between some rivers. There are three municipalities, in this region, whose their urban areas are situated above 400 metres of elevation: Caçapava do Sul, with 444 metres, Pinheiro Machado, with 436 metres, and Encruzilhada do Sul, with 432 metres. With an urban area above 300 metres of elevation, there are the municipalities of Canguçu, with 386 metres, Piratini, with 349 metres, and Santana da Boa Vista, with 306 metres. One of the highest points in this range of hills is Cerro do Sandi, with an elevation of 510 metres, located in the municipality of Piratini.
Climate
The climate of this region is subtropical, bordering on an oceanic climate, with mild to warm summers and cool winters, with frequent frosts and fog. The rainfall is well distributed throughout the year, but occasional droughts can occur and snow is uncommon. The last snowfalls occurred on September 4, 2006, and on September 5, 2008, in some municipalities of the region. The average annual temperature in Serras de Sudeste is between 16 °C and 18 °C, and the average annual precipitation is about 1,400 mm. In the areas above 300 metres of elevation, the hottest month, January, has an average temperature of 21 °C, and the coldest month, July, has an average of 11 °C. In the lower areas of this plateau, the hottest month has an average between 22 °C and 24 °C, and the coldest month has an average temperature between 11 °C and 12 °C.
Vegetation
This plateau is located in the ecoregion of the Uruguayan savanna, and consists mostly of grasslands, with low and herbaceous vegetation and areas of palm savanna, gallery forests along rivers, and enclaves of submontane forest. Small groves of cultivated trees by the silviculture and native trees are also found.
This region has been visited by many tourists due to the beautiful rural landscapes, with many inns among the hills. The city of Piratini, located in Serras de Sudeste, was the first capital of the Riograndense Republic, a former republic in the 19th century.
Economy
The main economic activities of the region are: agriculture, animal husbandry, mining and viticulture, with production of wines of high quality, due to the characteristics of the soil and climate. Tourism is also economically significant. The silviculture has had great economic importance, with the afforestation of grasslands with eucalyptus, pine and acacia, utilized in the logging industry.
Highways
There are three federal highways in the region: BR-116, BR-392 and BR-293.
